Stuck on the edge of Mordekaiser ult

I was playing a Summoners Rift match as Ahri. The enemy's Mordekaiser ulted me 3 times during the game. When I got ulted I tried to move to the edge of the circle and then use my ult/flash to get over a wall or to create space between Mordekaiser and me.

However when i touched the edge of the circle my character got stuck. This happend all 3 times I got ulted by Mordekaiser.

This unfortunate bug resulted in a dead Ahri which was her teams only hope towards a victory.