Just seen this on BBMF official Facebook page. Looks like it was the reduction gearbox and it's being sorted. Hopefully airborne soon.
Goodevening all a quick update on our Merlin issue. Today we received five serviceable reduction gearbox assemblies back from Retro, Track & Air and with their assistance all five were fitted four on the Lancaster and the other on PZ865 and as you can see the rebuild is progressing well at the moment. Look out for another update tomorrow evening. Paul B