Hmmmm?
1st guess, some e-liquid leaked & got into the mod onto the circuitry. May be no way to fix that.
2nd guess, dirty battery contacts. Try cleaning them by removing the batteries and wiping the contacts in the compartment with a bit of alcohol on a paper towel.
3rd guess, a fault in your coil or tank causing the mod's protection to kick in. Try swapping them.
4th guess, some e-liquid or something on your fingers got under the fire button, causing the mod to see 5 clicks instead of 1 press.
Just taking shots in the dark here. Anyone else have ideas?