Loud popping noise, damper pedal glitch on PR902

Hi there, so glad to find this place and hoping to find a solution! I have a Technics Digital Ensemble piano, model SX-PR902. I've had it for about 11 years and it was given to me before that. Not sure how old it is altogether. About a month ago during a piano lesson I was teaching the piano made a loud POP as though the speakers had blown or something. It startled us both but seemed to function fine after that. I was concerned but it didn't do it again that week and I didn't know what to make of it. A friend thought that maybe because I had an air conditioner plugged into the same socket that power surges in the ac unit might be causing the pop. I moved the ac to another wall, but the popping sound has continued, sometimes 2-3 times in a 4 hour teaching session. I have noticed that sometimes I can tell when it's going to happen because there will be a little buzzing that happens when you strike the keys that seems to build up to the pop. It's startled a number of my more nervous, young and autistic students and I've had to stop teaching until I can figure out what's going on or replace the piano. I have learned from various technicians in my area (San Francisco Bay Area) that this model isn't supported any more and that it can be very hard to replace. I have a technician willing to come to my home in two weeks to look at it for a minimum $200 charge. He said that if the power something source (sorry, not technical at all!) had to be replaced it would be an additional $500. I'm trying to figure out what the best plan is. Do I try to sell the piano and buy something else? Do I wait two weeks and pay upwards of $700 for a repair? Two weeks of lost revenue factors into this too. I would be grateful for any suggestions or thoughts.

Also, for over a year now sometimes when I turn the piano on all the keys sound as if I am pushing down the damper pedal. When I wiggle the wire in the connection I can usually get it to fix itself, but I kind of hate getting down on the floor at the beginning of lessons to fix the wire. Any suggestions there?

Thanks so much!

Olivia