ReusableThemeIT fails in Windows

[tltv]

Description of the bug / feature

Some tests in com.vaadin.flow.uitest.ui.theme.ReusableThemeIT fails only when run in Windows. Works fine with Unix systems. Test setup may have also something wrong as stated in this comment.

Minimal reproducible example

Run ReusableThemeIT.

Expected behavior

No failures

Actual behavior

Some tests fails.
Logs: https://github.com/vaadin/flow/files/14932165/log.txt (note: ignore '//' in assert message paths, that was due to typo in test and it's fixed already)

Versions:

- Vaadin / Flow version: 24.4-SNAPSHOT
- Java version: 20
- OS version: Windows 10

See more details after this comment: #19140 (comment)