I have the same 2 problems you described on my 04 RX330 AWD and the radio sometimes will change stations all by itself, as if the seek button is stuck. Electrical problems are hard to diagnose and fix, especially on older vehicles. Any ideas and suggestions will be greatly appreciated.

 

I have a cheap fix when the volume **** fails to work. It may sound like a caveman fix but it works for me. I take my fist and tap the left side of the radio and it starts to function. This doesn't happen very often so this fix works for me.

 

This started happening on my 2007 RX350. Turning the volume **** will not change the volume. The steering wheel controls work fine. I also noticed that sometimes if I push the **** in to turn off the radio that the CD's begin ejecting one by one. I may pull the **** off and try to clean the contacts.

I never have luck with these radios. They all seem to be a POS. My 97 Civic you needed to feather the volume **** just right to get it to work. Then my 04 Accord I have to solder something in the radio then eventually bought a re-manufactured unit.