Fabric Version: 0.14.18
Kotlin Version: 1.8.20
MC Version: 1.19.2
DML-Refab Version: 0.5.12 BETA

Steps to replicate

1. Obtain Deep Learner and a Zombie Data Model
2. Place Data Model in Deep Learner
3. Close deep learner
4. Open it up again

The slots will all be empty and no experience will be gained. As far as I know this makes the mod unplayable.

I ran into the same issue on Fabric 1.20.1 with version 0.5.14-BETA

The problem has since disappeared for me, but I have update this and other mods, as well as removing Starlight and Axes are Weapons, but they seem unrelated (?)

EDIT: and I removed "Old Potions", which I forgot to mention.

We once had this issue reported to happen due to Wilder Wild, although I'm not sure it's still an issue on their end or not. Perhaps other mods made mixins similar to theirs that also breaks the Deep Learner...? This requires more research.