Although it is rather off the track of your thread (!), here's the successful fix I have used on my radio, which has also sucessfully worked on another Mk1.

I initially made sure that my aerial was properly grounded by removing it, greasing up the bodywork connection points and putting a new, properly soldered connector onto the coax. This may not be necessary for the fix, but I believe actually led to part of my problem.

Looking at the data sheet for the tuner unit indicates it is an extremely sensitive item, and following some advice read on another thread here, I removed my aerial amplifier and reduced the length of my aerial by 50%. Result - clear and precise station tuning, good stereo image, excellent signal strength, faultless RDS operation.

I hope this makes you smile if it works for you