kayn passive stacks not counting bug

so i main kayn and i play him quite a bit, this bug is not happening rarely by any means.. alot of the times after hitting champion(s) those stack's "orbs" will be pulled into him but wont raise the passive bar at all.. i've been in moments where i had like 99% stacked, and then went to gank another lane and after the fight the circle didn't move even one bit.. like nothing happened.. again this is not something that happened to me once or twice.. its happening on a regular basis and im actually amazed it hasn't been addressed yet.. kayn already have a weak early game cause of how his kit works and the thing is that you basically can't get a form before 12 minutes even if you go 5-0-5 is already bad enough .. i guess the stacks count more as the time pass or something like that but the fact that you get 0 stacks some times even at later stages of the game can really set him behind for even a longer period of time..