I was reading description for the mod and saw that the creator used the DLL from 'Misc. Training by Haplo_X1', which has been updated for 1.5... So on a whim, I decided to delete the DLL from the gym mod and and copy and paste the DLL from the Training Mod and it worked! You can now once again tell a pawn to work out and they sometimes go and work out on their own!

I'm not sure if the skills/joy are going up though... haven't played long enough to check.

Anyway, I didn't buy the game from steam so I can't post the fixed version in the workshop but here's how you do it...

1. Download Get Rimped and Misc. Training Mods
2. Open Mod Folders
3. Open 1.4 folder in get rimped, Open 1.5 folder in Training
4. Open assemblies folders in both Mods
5. Delete dll file in get rimped mod
6. Copy dll file from training Mod
7. Paste training mod dll into get rimped's assemblies folder
8. add mod manually

Don't ask me how it works because I have no clue.