You can try and reset the preferences,
back to their default values.
To see if this helps.
Also,
creating a new user profile,
sometimes helps correct many issues.
You can create a new Gimp User Profile,
by renaming the current user profile.
In my case,
if I were to rename my current profile.
I would rename it something like,
.gimp-2.8_old.
The Gimp User Folder is typically located at:
C:\Users\Your User Name\.gimp-2.8
Once you rename the current profile.
Launch Gimp and it will create a new Gimp .gimp-2.8 User Profile Folder,
in this same location.
You can then see if this behavior continues,
with the newly created Gimp User Profile Profile.