I think I had deleted one or more sprite objects, added a few more. Saved then clicked 'x' to close and got the following:
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Construct 2 Check failure
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Check failure! This is probably a bug:
Releasing texture that has already been released; check all textures are loaded/released correctly
Condition: false
File: Projects\ObjectTexture.cpp
Line: 425
Function: void __thiscall ObjectTexture::GLReleaseTexture(class cr::GLRenderer *)
Build: release 63 (32-bit) checked
Component: Construct 2 IDE
(Last Win32 error: 0)
You are using a 'checked' release of Construct 2, intended for testing, which causes certain errors to be reported this way. Hit Ctrl+C to copy this messagebox - it's useful information for the developers, so please include it with any bug reports! Click 'Abort' to quit (unsaved data will be lost!),'Retry' to turn off messages for this session and continue, or 'Ignore' to continue normally.
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Abort Retry Ignore
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After reloading .capx and changing a few things, no crash happened, so can't replicate.
File is HERE.