r_ichigo: please make sure to get the latest runtime from the 4.0 branch on GitHub if you are exporting from Spine Editor 4.0.x. For Spine Editor 4.1.x, get the code from the corresponding branch.
When you update the code, also make sure to copy over spine-cpp
. That has the core datastructures and algorithms and is likely containing a fix in the latest version for your specific issue.