Appdesigner saves corrupt files - removes all callback functions

Title says as much as I can say. I wittnessed twice the following behaviour: when saving an app via the appdesigner, closing the appdesigner, opening said file, all callback-functions are missing. They are still referenced for each button, but the actual function entry is completely missing.

Extremely annoying. Has anyone else observed such behavior? I am using 2020a and Matlab itself did not crash...