Strange VHS Tape Wear

I'm going through and backing up old vhs tapes, and I've found that one of them is falling apart.

Or so I thought. When I watch it, after about five minutes, it slowly fades to static. But if I take it out, clean the vcr, put the tape back in and leave off from the exact same spot, it's all pristine again. For about five minutes anyway.

Is it the fault of my cheap vcr, or am I going to have to back this tape up five minutes at a time?

Thanks, will do. My vcr is an "Alba", which is pretty crap, but got the job done when someone broke my trusty old Philips and all I wanted was to watch tapes!