VBA Userform toolbox won't appear or stay visible/usable

OK, this is driving my crazy. I have been through all other threads on this and nothing has helped so I'm starting a new one.

Most of the time the Userform toolbox won't appear at all, on the very rare occasion I manage to get it then it goes as soon as I lose focus on the userform and nothing brings it back, I have spent hours looking through all the other proposed solutions (reinstalling Excel, finding it hidden behind other things and nothing works.

This problem only started a few months ago and I have used it successfully hundreds of times for years. I am actually a trainer so I teach Excel and VBA. I couldn't locate the .bak files that some people talk about deleting so that may be an option if someone can tell me where to locate them (none of the paths are valid as they are from 2006) but I am close to resetting the entire laptop to factory settings.

Any advice would be appreciated

Just to add a little more of a twist to this puzzle, I use three screens. If I move the VBA editor to the main screen and then choose to view the toolbar it appears and if I then move the editor back to the screen I want, the toolbox remains visible and I can move the toolbar to the screen I want as well. Once I take focus off the userform though the toolbar disappears again and the only way to get it back is to repeat the editor dragging process