I got the same issue, But it is since I have Lab3
This bug is for whole building.
If 1 research is completed. I cannot complete because the other one is still busy. So basicly you need to wait all research is done.
ITs already talked about many times its on the list for fixes! Theres only a Workarround right now. If the Research is completed you can hit dropdown in the reasearch window and choose every reasearch there you can manualy look for the completed one and finish it. If your fortress is high enough you can still research 2 things (same for expedition building etc.).