I had the same problem but in multiplayer. No one could join due to the infinite shaders loading.
Turns out it was caused by a few mods.
The problem was that this only appeared AFTER someone bought the machine from a given mod. So, in the end, we bought every machine available and checked after buying every ten or so if others could join or not.
Out of our 200+ mods, 4 were causing an issue. I don't remember the exact names, but it was a barrel, a front loader, a round baler, and a cotton harvester. No idea why those were problematic though.