Ok, a screenshot will be added down. Just wanted to say that if I install the 11.7 build 46 version, it doesn't have that problem.
I don't know how to put a screenshot here, so I attatched it as a jpg file. You can see there the main avant browser windows, and inside of it one tab that is open, not maximized. When I want to move that tab window in the main avant browser window, while dragging it with the mouse, I can't see the window moving, so I need to guess if I moved it to the desired place or not, and see the result only after I release the mouse button.
I hope I could clarify the problem, if not, let me know and I'll try to even make a short video and a link to it, to show you. For now I'll use an earlier version since it's ok there, but I guess you would wanna solve this bug anyway.
Thanks and have a wonderful day!