A bit late replying but yes it's likely the solder points. I'm no whiz at soldering and tried to repair mine without much luck. Stupid design imo. The have the switch mounted to a small pcb that's attached to the mainboard by 4 solder points. All on the leading edge, all on the same edge. So when you depress the fire button it places force on those joints until it acts like a hinge and eventually they crack. Tried to find the photos, I may have posted them somewhere on the forums here years ago.
Found it via a google search, unfortunately the cam I had at the time was shitty so it's blurry. This shows the switch board soldered to the mainboard.
For a teardown, Daniel at Djlsbvapes did one in his video on it.