Sans Culottes wrote:
Thanks for your suggestion. I have toggled that on and off a number of times, it is now set to off and the issue remains
Is it Mission Control being activated, or the window becoming full screen (another possible result of dragging a window to the Menu Bar)? If you're dragging a file, that wouldn't happen, but if you are dragging a window then ensure the setting in Desktop & Dock > Windows section, Drag windows to menu bar to fill screen is also off.
If you've done all of that and still have the issue, than as @Barney-15E suggests, contact the developer of the app/utility that you are using.