EDIT: Solved! Thanks to everyone for all of your assistance, I really appreciate the amount of people who put in time to help :D. My friend found out that apparently save scumming in multiplayer with even the slightest amount of cosmetic mods can mess up the game for the player doing the rolls, especially when later adding further mods. It worked to uninstall the game and entirely delete my game folder, a solution I hate using no matter the game, but nonetheless often a very effective one.
Recently, I got around to trying to play the game with my friends again. However, when i joined the host, I experienced an issue on my end, where it looked like all custom character had a Condition for "Alternate Form: Phase Spider", and one of us, a monk, for some reason also had a condition for Moonbeam, whilst Withers appeared to have Spirit Guardians: Necrotic. Along with this i was unable to use any action, with Hide straight up not activating whilst Throw and Attack triggered before immediately deactivating again.
This hasn't happened before, and reinstalling the game didn't fix it. To be clear, I often play alone with many more mods, but I made sure to check we were using the same mods and that my load order was correct.
Our mod list consists of the following mods in order:
0 - ImpUI (ImprovedUI)
1 - CampApproval
2 - Storm And Spectral Dice
3 - Better Containers
4 - Better Context Menu
5 - Better Inventory UI
6 - Better Target Info
7 - Better Topbar
8 - Better Tooltips
If any further information is needed, I'd be happy to provide as much as I can. All help appreciated.