Now there is a new problem with this receiver - drifting!
After 4 months of continuous use this unit has decided it wants to randomly move frequencies just slightly off the tuned frequency.
It is definitely the RX and not the band 1 TX as I can pick up the band 1 TX at home and the frequency is the same, but for the past 2 days been having a lot of new much worse problems with this receiver.
The fact that it's drifting slightly suggests to me that it might have never been running PLL as the frequency doesn't jump to another it slowly drifts and comes back again. Piece of s**t!

Sorry guys my mistake!!
There was a problem with the receive antenna and not with the receiver, only realised this because it got damaged a couple of weeks back by something in very heavy winds and it was causing a very strange problem and the receiver was drifting and we had to retune our PLL TX.
Has anyone had ever this problem before?
We changed for brand new receive dipole aerial and now perfect! But that was a very strange problem and other damaged dipole aerial was causing this "M" receiver to drift.
And also some good news! Now with the brand new receiver dipole the S/N ratio problem is no longer happening any longer either!
That was a very strange problem S/N meter going up and down with the music but with the new receive antenna no longer changing S/N ratio and just staying up very high!
It's very strange because even before the aerial got damaged it was causing problems with receiver but other 2 receivers used before it were fine so it made me think it must be new "M" receiver is the problem, but no it's now working a dream! :

~3L0~

Well done for finally getting to the bottom of it, you probably always had the issue but when the signal is strong enough its not noticeable.