TheBoxOfFun upvoted in favor of a 6K article, removed that vote after admitting changing it to the benefit of another 6K article, and then reverted this change two days later. See below for screen cap evidence:
Prior to the reversion, this would have been technically considered malicious downvoting. It's up to the contest team to determine if contest-related repercussions are in order. However, as the user corrected their downvote on their own and hasn't had any previous pattern of behavior, no disciplinary action will be taken at this time.
A PM has been sent to ensure the user is aware of the situation.