That is because the M3 loads dead transponders over a period of time so I make the channel list on the TM5402HD M1 then transfer it to the M3 via a USB stick,
So to overcome your problem load my latest channel list here with virtually no dead transponders:-
TM5402HD Ch list by William-1
In the future to reduce the addition of dead transponders use the Network Search on the Astra satellites @ 28.2E & 19.2E
Where you can manually update your channel list from here
News - FlySat Satellite Chart
Never do a Network search or Blind Scan with the M3 on 42 east,26 east 16 east & 7.2 west because due to the poorly compiled software you will get loads of transponders for the East beam of 42 east Middle East transponders from 26 east & Nilesat @ 7 west all are not possible to receive in the UK even with a 120 cm dish & 16 east goes mad & adds transponders in the 11700 to 12500 part of the Ku band that do not exist,
TM once tried to tell me that I was picking up Amos-5 @ 17 east after it ceased working