I encountered the same issue. I was planning to reinstall OS as restarting/shuting down/reinstall application did not help. This issue started happening after changing placement left to right in window titlebars. If the placement is changed from left to right/right to left, the flickering is appearing and menus in gnome tweak box are not registering/clickable. So, above solution worked for me. Resize the gnome tweak then change the placement setting then close it. Everything should be normal after that as long as you do not touch/move the settings of placement . Thanks, Xavier (xavierl) for solution.
I encountered the same issue. I was planning to reinstall OS as restarting/shuting down/reinstall application did not help. This issue started happening after changing placement left to right in window titlebars. If the placement is changed from left to right/right to left, the flickering is appearing and menus in gnome tweak box are not registering/ clickable. So, above solution worked for me. Resize the gnome tweak then change the placement setting then close it. Everything should be normal after that as long as you do not touch/move the settings of placement . Thanks, Xavier (xavierl) for solution.