I recently played a game with my mates, full premade.
About 15 mins into the game (Everything ran smoothly) 4 out of 5 of our team members crashed with the error in the picture. Our last member was fine (Might be cause he was on a mac?). Enemy team was fine. The only processes I was running alongside League was Spotify, Discord (with overlay) and Steam.
When all of us tried to rejoin, we crashed again after about 15 seconds or so.
Specs for info:
OS: Windows 10, fully updated
GPU: Zotac GTX 1080
Memory: 16GB of RAM