Sony Dynamicron L-750 U.H.G. video tapes

[B 4204 T3]

A while back, I bought a big collection of used Betamax video cassettes from the 1980s & 1990s from an elderly couple. They took really good care of them, and they are all in very good condition. I have spent the last few years playing them, and most of them still play very well, with excellent sound & picture quality; however, there are some tapes they had called Sony Dynamicron L-750 Ultra High Grade video cassettes that I am having problems with trying to play.



They come in a brown sleeve with yellow, orange, pink, purple, and blue horizontal stripes in the middle of it, along with this promotional statement on the back:



"Newly developed VIVAX magnetic particles give superior picture resolution and audio quality at every recording speed."



The problem that I am having with these tapes is that I can get them to load & start playing, but the picture quality is absolutely dreadful! They all have a lot of static in the picture, and sometimes, the picture is so grainy and snowy that it's difficult for me to even tell what is going on in the scene that I am trying to watch, and other times, the picture just cuts out entirely. Despite the bad picture, the sound quality is still satisfactory the entire time they are playing.



I've never had this problem with any other video tapes that I've ever played before, either Betamax or VHS. Many different brands of tapes came in the lot, and the confusing part is that only these tapes have the bad video quality, and all the rest of the tapes are good. Even the off-brand tapes still have excellent quality, unlike these tapes. Some of the recordings were taped at the Beta II speed, and others were tapes at the Beta III speed, which I know can make a difference, but they're all the same quality with these tapes.



Does anyone know what the problem is? Physically, they are all in the same good condition as the rest of the tapes. I was also able to rewind, fast-forward, and pause them without any problems. Could they have sticky-shed syndrome, or any design flaw which caused them to not hold up well over the years? I've tried to research them online, but I can't find very much information about them.



If any one is familiar with these particular tapes or knows anything about them, then I would really appreciate it. Thanks!