Epiphone ES 339 Pro Electronics PUP/switch issue

I've had the guitar for about a year now, and the problem started probably a month after I bought it and persists until now.
The issue: I lose the sound on either pup from time to time and I fix it by moving the pup switch back and forth until the pup that lost sound gains it back. sometimes it's the bridge pup but most of the time it's the neck pup. although I manage to make it work after some time it is really annoying and I've checked the switch and all solders seem to be intact.
for anyone who has faced the same/similar issue hope you can shed some light here
Thanks