DVD on Scart Passthough - no sound when recording ?

HI im not sure if this is a bug/feature or is just how it is being knew to the PVR world but ive got my DVD player attached to the VHS scart socket as it handy for the picture to be switched automatically when i switch it on (i have a very old telly with only one scart ).All has been working fine except yesterday whilst watching a movie a recording kicked in and i lost sound completley though the picture stayed , any thoughts ?