Tryndamere ultimate not working (possible interaction bug with WW)

Just played a match, usin my good ole' legendary Tryndamere skin killing teemos and things and then warwick shows up, ults me and I die while my ultimate is activated, it happened 3 times during the match. I could understand it not going on cooldown and just chalk it up to me not being quick enough to press R. But I made sure to ult at about 1/3 hp 1v1 vs him just to make sure and sure enough I died as soon as my hp reached 0 with more than 3 seconds still left on my ultimate.