I had this happen the other day. 2 stacks of Hobbled Dragon key and I couldn't move at all. Had to bullet jump as nothing else worked.

It reverts back to normal once you die, so I just had to get the capture target to shoot the shit out of me.

Looks like every single time you use Transference while wearing multiple Dragon Keys, you stack an effect (like when you double one of them upon picking up the artifact).

It's very noticeable when stacking Hobbled and you go reeeeeeeeally slow, or stacking Extinguished and do zero or 1 damage ticks vs. normal enemies.

I even get my UI refreshed showing the key name. Can you reproduce this bug?

Dragon Keys bug stacking their effects