Recording issues (?) with Matsui VP9608 VHS VCR?

Our VCR has started intermittently not fully recording over previous recordings - symptoms are that every few seconds (but at irregular intervals) the picture will degrade to static and the sound from "beneath" can be heard, lasting for roughly 3-10 seconds. When the picture's okay, it's as good as VHS gets, so I'm thinking it's not the play head/s; bought or hired tapes play okay, which makes me think it must be the record head/s. What about iffy tapes? We usually buy Emtec or Sony.
We use our VCR almost every day and are not in a position to be able to afford DVD or HDD recording (yet), so to be able to fix this and avoid buying a new machine - while they still exist - would be a massive relief! Any help would be much appreciated. Cheers.