[GAMEPLAY] can't get out of the base

i qued up for a ranked game,picked cho'gath and the game started. After loading i bought items and clicked to go top lane but my champion would just walk around in the fountain as if the wall for the first few seconds were still here even tho my team mates already left the base.one of the players told me to reconnect,so i did,and it didn't work, did it a few more times and it finally worked but because of my slow computer it was already 12th minute and the game was lost. and to add to it after the game ended i got a 5 game low priority que for leaving the game. I have seen this bug happen before and every time it ruined the game because one of the teams was short a player for at least 5 minutes.