Toshiba Combi issue?

Hi, we have a DVR19DTKB2 combi recorder which we are really pleased with.
There seems to be a video problem when playing back a program that we record on a cassette. The required program recorders but every minute or so on playback the display goes black then continues seconds later.
This doesn't happen on pre recordered videos only on one taped on the combi.
I know we don't use this facility much, but if it could be corrected any advice would be appreciated.
Thank you for your help.