Same issue here. Here's my report. Hopefully, there'll be something you can use to fix this issue. 

System: PS4

Character: Assassin - Sniper

Happened twice to me at the moment. Killed the great unclean one with fully charged longlas sniper shots while inoculator damage boost was in effect.

Then there was the cutscene with the demon getting evaporated by the pariah. Followed by a discussion between the player character and the tech priest. 

After that, Mission goal states to talk to alpha pariah, but the pariah cannot be highlighted nor interracted with. When moving around the mission area, i noticed the cogitator accessed earlier in the mission remains highlighted, but cannot be accessed either. Zoom function is non functional.

Besides zoom function, all seems to work like in combat situation.

i retried a couple of times. after reading the comments i also noted that my camera zoom was affected. i also noticed that if id run back to the cogitator it was highlighted yellow for some reason. on the third restart i did not take the additional info by the cogitator and was able to interact. this may not have been related. 

Thanks!