Yesterday I could play LoL without problems, today whenever I wanted to play a game I got a bugsplat after the champ select was finished, as soon as the loading screen started to pop up (together with a windows 10 tooltip to open the "game bar"). This would happen in every game mode, not just the newly enabled ARURF. The only thing that has happened was that windows 10 had performed an auto-update and reset the PC.
Work-around: In the windows 10 Xbox app, go to settings and turn off "Game DVR", this will prevent the tooltip from popping up which seemed to have caused the problem.
In the past this tooltip never gave me any problems