See a lot of RPG and LARP here. We're mostly board gamers and have left a table a couple of times in the last 8 years.
We played a Descent type board game 1 vs many where they booked "DM" to 2 tables and you had to wait for them to do one table then the next. We talked to the other players at our table and let them know we wanted to leave, but were willing to stay if they wanted with no issues. Ended up they felt the same we did. We told the person running the game how we felt and they apologized and offered to try to find someone, but we told them we were done and left.
This year we had a learn to play event and the 2 of us ended up on opposite teams each with a random person, not a big deal for us. The learn to play was staggered with another event by an hour so once we were an hour in the person running had to go teach another table. When you get into the meat of a game an hour in, that's not the time to leave new players. The random guys we were paired with then ended up arguing about every rule we didn't know, and we ended up leaving them at the table, with a "you guys don't need us to argue amongst yourselves." and we ditched.
Once three of us showed up to what ended up being 1v1 games so i was with a random person, not a big deal. The other 2 in my group quit half way through, they were playing together and didn't like the game. I stayed, even though i didn't care for it, because the person i was paired with really wanted to play the game. So i gave it my all and gave them a good experience.
I will always voice how we're feeling to who is running the game, if they are there, and if it effects another player will see how they feel about it and salvage it for them if i can.