Terrible you are having all these issues. I apologize for giving you hard time before. I thought you modified the radio with larger finals for more power. I am sorry.
I will say this though. I heavily modified my RCI2950. I never modified it for more power. As I upgraded components I kept the power output at factory levels. My goal was to gain enhanced durability and stability.
I think that if people would turn the rf output power down to 12 O'Clock or lower a lot of these issues could be prevented. Maybe "prevented" is the wrong word but it could prolong their life. No one drives their car or truck around at redline.
Less built in power and more bipolar external amps even HG's as I understand it can live a longer life than non-rf mosfets in rf amplifier use. This assumes though that the person running the external amp is not going to run a splatter box into it or over drive it or over volt it! I know I am wasting my breath telling people on this sight not to buy the 10M Export Radio with 100, 200, 400, 600 watts of power built in with cheap mosfets for use on CB but I am saying it again any ways!
None of these radio's have enough heat sink to actually get rid of the heat them make at factory levels and they are even worse once "technicians" get into them and start cranking them up them up to stupid levels like "11" aka Spinal Tap level. It is then in the hands of the owner to know that they should run them with the RF power knob set no higher than 12 O'Clock especially on AM.
Once you get to 100 watts nothing else really mattes until you get to what 500w or 600 watts??? So 140w or 150w is just stupid to no end at that point. It would be like taking an engine to 7000rpms if it has nothing else to give past 5400rpms it is an exercise in stupidity at that point. This is not aimed at anyone person either.
We see nothing but issues out of these "export radio's" especialy once they have been "tuned up" past OEM specified power output. This is nothing new but it is insanely common once bipolars went away and the mosfet's came to town! Even from the factory often the bias is not set right on these!