Do any of the mod's messages show up for the clients? If not then it sounds like the classic: https://spaceengineers.wiki.gg/wiki/Fixing_Download_Corruption

If they do show up, then can you guys test on a dedicated server (it's available in steam's tools, section), because I can test solo in DS but if it really requires a player-hosted server I'd have to find someone to test with, unless you guys are offering to let me join to see what's happening.

The messages show up on my own save files, when I run the mod.
The hosts sees the messages himself when he hosts, but I don't see the messages when I join him.
I'm not around today to test, but I might be later.