Reported a thousand times before. Seems to be a bug related to players with packetloss. Check your packetloss with /PL I think.
You should type /refreshtarget in this circumstance and it seems to fix the issue by recreating the target.
Also, for the love of god, please use a proper topic title. If every topic title is ‘Bug’ how the hell am I supposed to know what topics I’m looking at?!