Lock on + parry, broken interaction

Playing on PC, with gamepad. Playing as a rogue, doing Taash's introduction quest.

I started using R3 button to manually lock onto enemies, which helps a lot with parrying, but whenever I parry an attack it automatically switches my target to a different enemy.

It seems that whenever an enemy gets "knocked out/down" it auto-switches away from that enemy - however that defeats the entire purpose of parrying, which is that I want to continue targeting that same enemy in order to carry out a follow up attack! Instead I get locked onto a target that could be several meters away, and my follow up attack hits only air.

This is extremely frustrating, especially considering how difficult parries can be when you don't lock onto your target. I've tried turning the 'auto lock melee' setting off and then on, and I don't see a difference.