Hi @Northernsoul65 sorry to hear the recordings are gone.
Which BT bv box is it and roughly how old is it ?
Such incidents do get reported on the forums occasionally.
Sometime a box might startup in maintenance mode - this (to me )suggests that the box has failed to launch the Youview application from the hard drive probably due to a hard drive corruption.
Your experience seems to be when a software update is being rolled out, Some updates are pretty straightforward whereas others may require quite a lot of hard disc activity. Suspect that a problem occured and the data that should have been preserved couldn't be and the box effectively required setting up again.