You're probably already aware that the 11.16 scenario packs don't work in 12, but thought I'd report anyway:

I just downloaded a fresh copy of 0.12.0 (64 bit zip package)
- I logged in
- Updated scenario pack to 11.16
- Click Play
- Click Custom Scenario
- Click Scenario-Pack/Supply
- Click create ...

This mod caused a multi-player error every so often and on save (which prevented saving) which we got from the Shadow ModPack.

We "fixed" it, but we really don't know what we're doing so take it with a grain of salt. The issue is in control.lua which references game.player

game.onload(function ...