DNA250C locks up, instead of firing

[AMDtrucking]

Lately, one of my DNA250C, instead of firing, goes into a lock up mode.  I would unlock it, press the fire button and it locks up again. Any ideas?

 

[retird]

What happens when you unlock it and then momentarily touch the fire button (don't hold it in as if normally firing it)?  Does it still lock?  Maybe a dirty contact in the fire button?

[AMDtrucking]

4 hours ago, retird said:

What happens when you unlock it and then momentarily touch the fire button (don't hold it in as if normally firing it)?  Does it still lock?  Maybe a dirty contact in the fire button?

I tried, I doesn't lock up, but it doesn't fire either. I suspected the switch itself too, but when I bypass the switch, by  shorting its legs with a pair of tweezers, the same thing happens - board goes into lock up mode.