112RD50 mystery reverb issue….

Hi folks. This is my first post. I’m grateful for the forum. It’s always uplifting to run into another MusicMan amp fanatic out in the road. So, I’m curious if anyone else experiences this issue. I’m not a tech but a working musician. Several techs have already attempted and failed at solving this issue. Basically, when I turn my amp on, it takes 10-20 minutes before the reverb works. During this time, the sound coming out of amp when playing is slightly distorted and if I staycation a chord, there’s a slight audible “sizzle” sound (distorted). After the reverb finally kicks in, I’m good to go. My tech noticed a particular wavelength of interference (on his monitor) during this warm up time but he could not determine the source. I’d love to get some advice from you that I can share with him as he is planning a deeper dive troubleshooting in the next weeks. Thanks so much.