Failed to load mods: Error while loading entity prototype "baron-heat-tower" (underground-belt): tile_width must be 1 but it is 2

Turns out that that is one of at least 3 errors I discovered (patched that and tile_height must be 1) and the heat reactor is broken. (something about 1 != 12).

I'm not surprised the heat towers have failed. I haven't patched them since Factorio fixed the heat transfer issue back in v0.18.

I'll take a look this week.

I've fixed the issues. Apparently underground belts can no longer be 2x2, so I've shrunk the towers to 1x1. The other issue was that the watermark was causing a failure when being added to certain structures with the new variation count (i.e. nuclear reactor.)

Everything seems to be working now, but give it a try and let me know.

Well, it loads, which is better than it started out, but it breaks when you research everything in sandbox/editor mode. It also breaks when you click a faction:
LuaEntity doesn't contain key character_logistic_slot_count, and it quotes register-handles.lua:37

I wish lua-api.factorio.com weren't down right now. I have no idea what they changed the value to.

Updated again. I removed the character_logistic_slot_count check, which means you'll lose your logistics requests on respawn, but at least it won't crash. I also found a crash error when attempting to select a faction in sandbox mode, so I fixed that.

However, I was unable to recreate the sandbox crash by researching everything. Are there any other mods you're using? Are there specific mods settings you are using that causes the crash?

I think you fixed it because I just loaded into a sandbox map and it didn't crash.

Woohoo! I'm glad it's working again!