If you open F4 (the drugs panel), you won't be able to close it by pressing "Close". You can exit out of the panel by pressing F4 again. Date: 23/12/17 Time: (14:49) +2
I have confirmed this bug.
Debugscript doesn't say anything.
@The_Moose this is your speciality
I've seen the same thing in more places, could be related to GTWgui