diff --git a/distributed/scheduler.py b/distributed/scheduler.py
index 3fa84b19878..0a4c8a6aa28 100644
--- a/distributed/scheduler.py
+++ b/distributed/scheduler.py
@@ -2751,8 +2751,7 @@ def transition_processing_memory(
 
             if ws != ts._processing_on:  # someone else has this task
                 logger.info(
-                    "Unexpected worker completed task, likely due to "
-                    "work stealing. Expected: %s, Got: %s, Key: %s",
+                    "Unexpected worker completed task. Expected: %s, Got: %s, Key: %s",
                     ts._processing_on,
                     ws,
                     key,
@@ -2849,7 +2848,7 @@ def transition_memory_released(self, key, safe: bint = False):
             worker_msg = {
                 "op": "free-keys",
                 "keys": [key],
-                "reason": f"Memory->Released {key}",
+                "stimulus_id": f"memory-released-{time()}",
             }
             for ws in ts._who_has:
                 worker_msgs[ws._address] = [worker_msg]
@@ -2949,7 +2948,11 @@ def transition_erred_released(self, key):
                 if dts._state == "erred":
                     recommendations[dts._key] = "waiting"
 
-            w_msg = {"op": "free-keys", "keys": [key], "reason": "Erred->Released"}
+            w_msg = {
+                "op": "free-keys",
+                "keys": [key],
+                "stimulus_id": f"erred-released-{time()}",
+            }
             for ws_addr in ts._erred_on:
                 worker_msgs[ws_addr] = [w_msg]
             ts._erred_on.clear()
@@ -3027,7 +3030,7 @@ def transition_processing_released(self, key):
                     {
                         "op": "free-keys",
                         "keys": [key],
-                        "reason": f"processing-released-{time()}",
+                        "stimulus_id": f"processing-released-{time()}",
                     }
                 ]
 
@@ -4364,9 +4367,9 @@ async def add_worker(
                         worker_msgs[address] = []
                     worker_msgs[address].append(
                         {
-                            "op": "free-keys",
+                            "op": "remove-replicas",
                             "keys": already_released_keys,
-                            "reason": f"reconnect-already-released-{time()}",
+                            "stimulus_id": f"reconnect-already-released-{time()}",
                         }
                     )
 
@@ -4793,7 +4796,7 @@ def stimulus_task_finished(self, key=None, worker=None, **kwargs):
                 {
                     "op": "free-keys",
                     "keys": [key],
-                    "reason": f"already-released-or-forgotten-{time()}",
+                    "stimulus_id": f"already-released-or-forgotten-{time()}",
                 }
             ]
         elif ts._state == "memory":
@@ -6018,7 +6021,7 @@ async def delete_worker_data(
             await retry_operation(
                 self.rpc(addr=worker_address).free_keys,
                 keys=list(keys),
-                reason="rebalance/replicate",
+                stimulus_id=f"delete-data-{time()}",
             )
         except OSError as e:
             # This can happen e.g. if the worker is going through controlled shutdown;
@@ -7899,7 +7902,7 @@ def _propagate_forgotten(
                 {
                     "op": "free-keys",
                     "keys": [key],
-                    "reason": f"propagate-forgotten {ts.key}",
+                    "stimulus_id": f"propagate-forgotten-{time()}",
                 }
             ]
     state.remove_all_replicas(ts)
diff --git a/distributed/spill.py b/distributed/spill.py
index 5d90361d170..2c849c2447e 100644
--- a/distributed/spill.py
+++ b/distributed/spill.py
@@ -4,14 +4,11 @@
 from functools import partial
 from typing import Any
 
+from zict import Buffer, File, Func
+
 from .protocol import deserialize_bytes, serialize_bytelist
 from .sizeof import safe_sizeof
 
-try:
-    from zict import Buffer, File, Func
-except ImportError:
-    raise ImportError("Please `python -m pip install zict` for spill-to-disk workers")
-
 
 class SpillBuffer(Buffer):
     """MutableMapping that automatically spills out dask key/value pairs to disk when
diff --git a/distributed/tests/test_failed_workers.py b/distributed/tests/test_failed_workers.py
index 8e5d01167d0..2b6d5149a2a 100644
--- a/distributed/tests/test_failed_workers.py
+++ b/distributed/tests/test_failed_workers.py
@@ -488,7 +488,7 @@ def sink(*args):
         # artificially, without notifying the scheduler.
         # This can only succeed if B handles the missing data properly by
         # removing A from the known sources of keys
-        a.handle_free_keys(keys=["f1"], reason="Am I evil?")  # Yes, I am!
+        a.handle_free_keys(keys=["f1"], stimulus_id="Am I evil?")  # Yes, I am!
         result_fut = c.submit(sink, futures, workers=x.address)
 
         await result_fut
diff --git a/distributed/tests/test_scheduler.py b/distributed/tests/test_scheduler.py
index f93499fb421..fdac636e0c1 100644
--- a/distributed/tests/test_scheduler.py
+++ b/distributed/tests/test_scheduler.py
@@ -2476,8 +2476,6 @@ async def assert_memory(scheduler_or_workerstate, attr: str, min_, max_, timeout
     client=True, Worker=Nanny, worker_kwargs={"memory_limit": "500 MiB"}, timeout=120
 )
 async def test_memory(c, s, *_):
-    pytest.importorskip("zict")
-
     # WorkerState objects, as opposed to the Nanny objects passed by gen_cluster
     a, b = s.workers.values()
 
diff --git a/distributed/tests/test_spill.py b/distributed/tests/test_spill.py
index 8735f1acbdf..d013b141158 100644
--- a/distributed/tests/test_spill.py
+++ b/distributed/tests/test_spill.py
@@ -1,7 +1,5 @@
 import pytest
 
-pytest.importorskip("zict")
-
 from dask.sizeof import sizeof
 
 from distributed.spill import SpillBuffer
diff --git a/distributed/tests/test_worker.py b/distributed/tests/test_worker.py
index a92700b053c..81e25d8d039 100644
--- a/distributed/tests/test_worker.py
+++ b/distributed/tests/test_worker.py
@@ -2444,7 +2444,6 @@ async def test_hold_on_to_replicas(c, s, *workers):
         await asyncio.sleep(0.01)
 
 
-@pytest.mark.flaky(reruns=10, reruns_delay=5)
 @gen_cluster(client=True)
 async def test_worker_reconnects_mid_compute(c, s, a, b):
     """Ensure that, if a worker disconnects while computing a result, the scheduler will
@@ -2513,7 +2512,6 @@ def fast_on_a(lock):
         await asyncio.sleep(0.001)
 
 
-@pytest.mark.flaky(reruns=10, reruns_delay=5)
 @gen_cluster(client=True)
 async def test_worker_reconnects_mid_compute_multiple_states_on_scheduler(c, s, a, b):
     """
@@ -3089,6 +3087,7 @@ async def _wait_for_flight(key, worker):
         await asyncio.sleep(0)
 
 
+@pytest.mark.xfail(reason="#5406")
 @gen_cluster(client=True)
 async def test_gather_dep_do_not_handle_response_of_not_requested_tasks(c, s, a, b):
     """At time of writing, the gather_dep implementation filtered tasks again
@@ -3122,6 +3121,7 @@ async def test_gather_dep_do_not_handle_response_of_not_requested_tasks(c, s, a,
     await fut3
 
 
+@pytest.mark.xfail(reason="#5406")
 @gen_cluster(
     client=True,
     config={
diff --git a/distributed/worker.py b/distributed/worker.py
index 06d914e3838..dc76d30a09a 100644
--- a/distributed/worker.py
+++ b/distributed/worker.py
@@ -1600,7 +1600,7 @@ def update_data(
             self.batched_stream.send(msg)
         return {"nbytes": {k: sizeof(v) for k, v in data.items()}, "status": "OK"}
 
-    def handle_free_keys(self, comm=None, keys=None, reason=None):
+    def handle_free_keys(self, comm=None, keys=None, stimulus_id=None):
         """
         Handler to be called by the scheduler.
 
@@ -1611,14 +1611,14 @@ def handle_free_keys(self, comm=None, keys=None, reason=None):
         still decide to hold on to the data and task since it is required by an
         upstream dependency.
         """
-        self.log.append(("free-keys", keys, reason))
+        self.log.append(("free-keys", keys, stimulus_id))
         recommendations = {}
         for key in keys:
             ts = self.tasks.get(key)
             if ts:
                 recommendations[ts] = "released" if ts.dependents else "forgotten"
 
-        self.transitions(recommendations, stimulus_id=reason)
+        self.transitions(recommendations, stimulus_id=stimulus_id)
 
     def handle_remove_replicas(self, keys, stimulus_id):
         """Stream handler notifying the worker that it might be holding unreferenced,