Is my JVC HR-S7600EU VCR worn out?

[hysteriah]

My JVC HR-S7600EU has started to play tapes with jumping fields/frames from time to time. It may play flawless for a few minutes, then it starts jumping a few frames... then it plays flawless again for some time before it starts jumping again. It happens with every single tape I've tried, from the most worn ones, to perfect tapes without any sign of wear. It happens with the built in TBC turned on and off. I've tried to turn B.E.S.T. off and I've also tried manual tracking.

I've also tried cleaning my videoheads carefully by folowing this method (from 6:50min) in this video:
https://www.youtube.com/watch?v=B7we2kgtCOY
It was no noticeable difference :-(

Is this a common problem with a JVC HR-S7600EU when it gets "old"?
Is my VCR heads worn out? ...or is it just an adjustment that has to be done?

Sorry for my bad English

[volksjager]

is the pinch roller in good shape?
clean all the old grease and relube the mech and pinch roller pivot
clean the capstan really good too

[hysteriah]

Thank you very much for the reply
The pinch roller looks in good shape. I've tried to clean it carefully now together with the capstan. Didn't have any effect :-(

...and there's another thing. There's a lot of crackling noise in the sound on pretty much all tapes played back with stereo sound. Switching to mono makes the crackling noise disapear.

I guess all my problems must be caused by bad tape path alignment?