There is a good chance that you can open the Project in 3.8.13-beta, then export the JSON file (with Nonessential data
checked). Load up 3.8.11-beta and Import Data
.
If this doesn't work for you, Spine makes backups of your projects while you are working. You can find the backup folder by going to Settings
and then Files
and click Open
next to Backups.
I hope this helps!