Guild Wars 2

I recently (30 min ago) played against a Ranger/Druid in Ranked/sPvP that I couldn’t complete the finish-skill on. It’s not like I was interrupted or stunned in any way that made me question what was happening, but the finish-skill didn’t do anything.
I noticed after a few failed attempts that whenever I tried to finish the ranger, my character instantly faced the direction of his pet. The down animation played out fully but the ranger didn’t get finished after I completed the finish and I just stood there like a fool trying to do it again. Targeting the ranger didn’t help.

I have never seen or faced another ranger that made the finish-skill act like this before, and I asked a ranger friend to see if that pet have any weird taunt/focus-changing abilities but it didn’t.
The ranger was using the Bristleback pet and no other ally or enemy was there during the first times it happened.

Also worthy to note is that the ranger was still in downed state after I finished trying to finish them. So they didn’t get resurrected by their pet meanwhile.

I was playing on Necromancer/Reaper and the finish-skill acted the same way for both in Reaper’s Shroud and without.

Has anyone else experienced similar things for other characters when trying to finish them? Am I missing something and this is actually not a bug, but just some weird options that is screwing over the way my character acted? (although this never happens with other characters/rangers I try to finish)

Cheers.