Game crashes in game [GAMEPLAY] [CRASHES]

I get into a game without any trouble but it randomly freezes after between 4 and 7 minutes. Just stops. I end the process in the task manager, log back in, reconnect. and the game is fines afterwards.

Obviously I have stopped playing ranked games until this is fixed but I keep trying different things At one time I found an error "An unknown DirectX error has occurred and League of Legends can't start." but having exhausted all the fixes for that and no difference, I now think this is a red herring caused by me trying to start again too quickly after terminating the application to fix this problem as nothing I have tried so far has helped.

Can anyone point me in any direction to help with this? Can I get access to any debug info for example? Has anyone seen this before?

I have not had any problems like this before and it's killing me not being able to play as I would like to as I don't like letting my team down so early in the game.

Many thanks.