Braum passive reset

I noticed during a game yesterday that another champion, namely maokai reset braum's passive after it disappeared just frames before, it was at three stacks but the duration ended, however his ( 's) next auto landed and proc'd winters bite passive and it started a one stack again, braum was dead at this time having died during the fight. i am unsure which champion this was against but it was either Zed or Vlad because it happened last night and i was tired. The Maokai also noticed this occur and stressed his confusion. I am pretty sure this is a bug.