Regarding the radio and antenna. Maybe "trigger" circuit in radio is going bad. Symptoms similar mine to yours. Trigger is blue wire at antenna and back of radio. Search "antenna trigger wire" and "radio removal" for more info & pics if you DIY.

You mentioned engine wire harness replaced and "other issues". Although not for CEL, the Battery aka "B" Harness if not replaced could cause problems.
"B" Harness connects:
Oil level = Brown/Black [left side, front, bottom of oil pan]
Oil Pressure = Brown/Green [left side, below oil filter]
Solenoid = Purple/White [on starter].
Main battery cable is usually ok. It's the smaller wires that have bad insulation. If handy you can easily replace them. Be careful with junction block to reuse & solder ends to wires.

Bob
PS Good to disconnect battery when messing with B Harness