Fairly light compared to many rpghorrorstories but wanted to share this from a few years ago.
I joined a group in progress as the 5th player character. They told me that they weren't a super serious group but didn't want any joke characters which was no problem.
Everything seemed on the up and up. 3 of the other players definitely were playing more seriously in that they were very much into the rules and making powerful characters. The other player was more along for the ride type guy but not really a focus of this story. But I like playing more support focused characters so it didn't bother me too much. I was fine with letting them do big damage while I kept them going as a more support role.
Eventually after a couple of sessions we had a battle that was going rough and spread the group out a bit to deal with threats at multiple ends of a board. I was with another player and was moving to return to the main group after finishing up on one end of the board. I moved next to the other player and didn't want to dash and end out in the open so I stopped and since I had extra spell slots at the time I used Cure Wounds on the other player to give them some extra health.
The other 3 people started to groan and complain that I was wasting my turn and spell slots and why in the world I would take Cure Wounds as a spell to begin with. I tried explained myself but it seemed to not ease them down. We continued on and finished the session but I felt something was off.
Turns out I was right and something was off. Apparently I wasn't performing good enough for the 3 players more into the game side of things. They were complaining that I wasn't doing enough and focusing too much on support and being too much of a joke character. They basically were upset that I wasn't playing clerics the way they wanted. I wasn't taking every optimum spell but I thought I was holding enough in my own for what I wanted. I know Curr Wounds wasn't the best spell but I wasn't this level of response.
The next session, they told me the exact spell list to prepare and how I should be playing my character. Including what actions I should be taking every single turn. Every time I wanted to do something different, I had to defend my action. Major backseat playing. It grew tired quickly and by the end of the session I was exhausted. I talked to the DM and he said his hands were tied.
Unfortunately, I decided to back out of that campaign after we couldn't come to an agreement. No idea what happened to that group.