This sounds like a crash occurring in the Spine Godot runtime when a 2D Fx sequence (image sequence attachment) reaches its last frame. A few things to check and try:
Make sure your spine-godot runtime is up to date
This type of crash on sequence end is the kind of issue that tends to get fixed in runtime updates. Make sure you are using the latest commit from the spine-runtimes GitHub repository for the branch matching your Spine editor version. You can check the repository here: https://github.com/EsotericSoftware/spine-runtimes
Also make sure that the spine-cpp files bundled inside the Spine Godot plugin are equally up to date, as an outdated spine-cpp copy can cause crashes independent of the rest of the plugin code.
Check your spine.log for clues
If you can reproduce the crash in the Spine editor itself (not Godot), check the log file before restarting Spine, as it gets cleared on each launch:
- Windows:
%UserProfile%\Spine\spine.log
- macOS:
~/Library/Application Support/Spine/spine.log
- Linux:
~/.spine/spine.log
The behavior you describe is notable
The fact that it crashes on the first playback at the last frame, but works fine on subsequent replays when triggered via signal, suggests a possible initialization or first-frame cleanup issue in the runtime rather than something wrong with your Spine project setup. This pattern is a good clue to include if you report it.
Check for hs_err_pid.log files
If Godot is crashing hard, check the Spine installation directory for any hs_err_pid.log files which can provide more detail on the nature of the crash.
Could you share which version of spine-godot/spine-runtimes you are using, and which version of Godot? That would help narrow things down significantly.
