Cateye EL320 switch glitch

Today, in muggy conditions, my Cateye EL320 front light started
playing up. The switch previously had three positions, on, blinking,
long press for off. Now it has somehow reset itself to Change
batteries, on, on, on, permanently off until batteries are removed and
reinserted. Basically it is unusable unless I want to take it off the
bike, open it, remove four batteries, replace four batteries, close
it, fix it back to the bike -- every time I want to use it.

Any ideas of what happened? How I can restore normal service? It's a
light I really like and use day and night.

Thanks.

Andre Jute
I'm not a know-all. I don't need to be. I know who to ask.