Fiddlesticks at Dragon pit

So I was playing fiddlesticks and enemy team started Elder dragon. I was next to a wall and I pressed my R. Then Talyah used her ult and my ult landed directly on her wall. I got knocked out of the dragon pit even if I ulted directly on dragon. I was not even close to a wall but I got knocked back over it.

My ult ----> middle of the dragon pit ---> Talyah wall also in the middle of a pit ---> Got knocked way back where I started channeling my ult

Hope I explained right