It's difficult to be specific because you haven't posted enough information about stuff like the connection method, what channel you use for playback, whether the VHS tapes are new or previous recordings, the model of the TV etc etc. But as a starting point I'd suggest you get the Tosh combi hooked up to your TV via SCART and (if possible) set menus for the connection to be Composite Video (A.K.A. CV, CVBS, Video, PAL) on both devices. This is the lowest common denominator so should give consistent results. Make sure to switch the TV to the corresponding AV channel for that SCART input.
Come back to us once you have done this and tried playback of DVD & VHS.