White stains in VHS picture, fades with successive playback?
 

Well, that is it. I have a really old VHS, probably 30 years old thing by now. I put in a low end VCR just for playback porpuses and I could barely see a thing cause the picture had some small horizontal white stains. It was really annoying, but I was too lazy so I left the VHS running and tried to see the video anyways.
Sound was OK though.
At a few points the whole picture had some sort of white noise which lasted for a couple seconds.
Interesting thing is that when I paused the VHS, picture was clear like it should be. After watching the whole video I rewinded it, and then some of the stains had gone and picture was clearer.
I suspect the VHS could have had some sort of dirt, but I'm not sure this is the cause. What do you think?
If so, could now the heads of my VCR be dirty? Would be harmful if I insert another VHS in a VCR with dirty heads?

Here's a good example of what I described above, only difference is my VHS had a lot more of these stains:
https://www.youtube.com/watch?v=RM-z_cW20Qo

Those aren't stains.

That exact Youtube image looks like total crap, and has
- likely tracking noise (white streaks)
- possible head damage noise (white streaks)
- horrible timebase errors, wiggling all over the place
- chroma noise

This is probably not dirty heads, but damaged heads.

Which VCR do you have? You really need to use a high-end VCR. Otherwise you're just wasting your time, as quality will be awful, unwatchable, and not enjoyable.

Thanks for answer. Well, as I stated above I was using a low end VCR (a crappy one). And I had that problem with 2 very old VHS tapes (late 80s maybe). Yesterday I saw an early/mid 90s VHS with the same deck and picture was just fine (no white streaks or something). That's why I guess the previous VHS might have been dirty. They hadn't been played in a long time perhaps, I guess they were coming from a former video store.