Just recently I've had a problem where the application menu in KDE Plasma 5 stops opening. The little icon seems to flash and a right click opens the context menu, everything else seems to work but I have no open menu to select programs etc from. Once it happens I have to logout and back in to get it working again. I have not seen any crashes in the log. Seems to have happened when I have quite a few programs opened.

Not much to go on I know but has anyone seen this or have any ideas please?