New Radios showing low DB

Hi, we have a whole batch of new 5700 Subscriber Modules that are showing a DB reading that is a lot lower than a similar 5700 radio purchased previously.
If we put one of the new radio’s in the same position as one of our older radios, the older one will show a DB setting of 74DB and the newer one will show a DB of 78.
I have checked that the firmware is the latest and the boards are version 9.
Not sure why these are different, any one else struck this and anyone know of how to fix them ?
We need to cover long distances so these radios are no good to us in there current state.

One of our 5200 SM became to operate with DB 4 less and higher jitter after a month of work. We had replaced it with a new radio.