Olaf ragnarok(ult) bug when interacting with illaoi

The situation goes like this 1.Olaf ults and runs 2.Illaoi uses E and pulls his spirit 3.when Olaf exits that range he is slowed!!!!!! This happened to me in a ranked game and I was easily slained. Tf illaoi and tryndamere chased me and I ulted to escape tryn's w and tf's yellow stun card...it worked but when illaoi did that e.....I was slowed after exiting that range and my ult was still on....Olaf was red in color