Spine.log warns "WARNING: Some hotkeys were not recognized". I triggered it by defaulting Hotkeys in Spine 4.2.08 beta , saving the setting, then opening Spine 4.1.24. Defaulting the Hotkeys in Spine 4.1.24 stops the warning when opening the same version again.
Switch back to 4.1.24 from 4.2.08 beta Hotkey
This happens when going back a major version, because the older version doesn't have the hotkeys from the newer version. We can avoid it by bumping the version number on the hotkeys (the files are named hotkeys-1.txt, hotkeys-2.txt, etc), but then you'd have to manage multiple hotkeys files.