Svelte 5: Transitioned out elements don't come back in if the transition does not complete

[BradenC]

Describe the bug

Items that transition in and out of a page may get stuck if the transition starts and ends too fast.

Reproduction

REPL

Move your mouse slowly across the red squares, and the green ones will fade out and back in correctly.
Move your mouse a bit faster and the green squares get stuck, sometimes never coming back in.

Logs

No response

System Info

System:
    OS: Linux 5.15 Ubuntu 20.04.6 LTS (Focal Fossa)
    CPU: (12) x64 AMD Ryzen 5 1600 Six-Core Processor
    Memory: 5.00 GB / 5.79 GB
    Container: Yes
    Shell: 5.0.17 - /bin/bash
  Binaries:
    Node: 20.13.1 - ~/.nvm/versions/node/v20.13.1/bin/node
    npm: 10.5.2 - ~/.nvm/versions/node/v20.13.1/bin/npm

Severity

annoyance

[7nik]

Isn't it the same as #12033?

[henrikvilhelmberglund]

Fixed by #12321.