If you smack it and it works again you have a NEARLY broken wire in there somewhere OR a bad pot. Give each wire a yank at the solder joint until you find a broken one. If not, work the pot to see if that's the problem
Plugging into the irig is just councidence.
'73-4 Ampeg V4B, Ampeg PF350,PF115HE, PF115LF, 115 Traynor, 1962 Fender Jazz, 75 Gibson G3, '10 Squier VM Jazz, Squier CV 60's P Sonic, Squier CV 50's P blonde, Epiphone Thunderbird IV