Hi everyone.
I have this exact same problem.
I read all the comments and i see there is no “fix” for this yet.
I cant recall since when i started having this problem but is not for a long time.
It´s terrible not being able to change/swap individual instruments from the browsing panel.
I unregistered the soundbanks, i uninstalled and re installed GA5, i deleted preferences and nothing seems to work. In my GASE5 all ok.
Windows 10 20h2
Cubase 12.0.50 (updated today)
Groove Agent 5 .1.11.176