Solved Sticky keys stops working on browser launch

I like to type with one finger when my dog is on my lap. Recently the shift key stops working as a sticky key in any browser. It often works once but then stops. The shift key still works in Notepad. Ctrl, WIN and Alt keys are not affected. If I hold the shift key down it works as normal.
I have tested this with Edge, Brave and Firefox.

Just to add, this behaviour seemed to vary and only persisted in Edge. I tested it in Safe Mode and the problem disappeared! It's been fine for two days.