Hello everyone. Sad to see all of these issues over the years.
I am having a slightly similar problem, except the filter select knob does not appear to impact any sound change when moving between LP HP BP Notch. I do, however, get sound out of selecting each mode.
At first, I thought I was having a sound level issue. Then, after more investigation, I discovered that the filter selection knob is not working as expected. Also, another odd aspect of my problem is that if I put the cut off frequency in ~12 o-clock and crank up the resonance, the sound comes BLASTING out.
I wondered if anyone else saw something similar to my issue and if replacing the Filter Mode rotary knob did the trick.
Thank you for your help.
UPDATE: After reading the forums and playing with my filter selection knob, I was able to hear it pop and blast some additional sound through, so I think this is my problem. Just ordered a new switch based on xanderhing reference, the SR1712F-0204-20F0A-N9-N-027, from Mouser:
https://www.mouser.com/ProductDetail/Alpha-Taiwan/SR1712F-0204-20F0A-N9-N-027I will report back how it goes.