Hello,
Seems kind of related, I'm on 3.6.52 on Win10, and I saw quite the same behavior.
I create a new spine file, then attempt to build a path.
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It happens when I drag drop a point, not when I just click to create one.
Spine freeze to death.
When I only click, it works well:
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I tried on Mac OS El Capitan, when drag and drop a point, the path is fucked up also, but the Spine software doesn't crash.