Hi.
I'm on version 8.0.5 and it looks like #1376 is still an issue:

Same thing is happening to me, I'm getting the Blindness 2 debuff from tar slime attacks that doesn't go away after killing the slime, prevents sprinting, and is not removable with commands. There is no persisting blindness effect however, it's just that the debuff is still shown and somehow sprinting is still disabled. To get rid of it without dying I need to log out of my world and back on.