Sup man! I casually discovered how to close the Blablabla window. At least in the stash
Gun with the blablabla window opened, put gun into the stash, right click, disassemble, now I got the lower and the Upper (might not work with every gun, now that I read this) I double clicked the upper to get a scope, put the upper and the lower together again, and the Blablabla window became a normal inspect window.
I just put the weapon together again and inspected to the blablabla window, right clicked the weapon, disassemble and It fixes itself, the stats appear in the window and you can close it. I guess there is some workarounds.
I hope it makes sense and it works.
Cheers!
Edit: Putting the grip into the gun makes the inspect window disappear, so if you inspect it again you'll get the Blablabla window.
Without the grip you can't use it, but as soon as the gun is "usable" it breaks again.