This question has been posed to me a few times lately, so I'll give a short answer real quickly right here...
And lastly, I remember reading something you wrote ages ago about how the Panasonic AG-1980 can be kinder to VHS-C tapes than the JVC machines. Just curious...why is this? I use the same motorized JVC adapter you do, and when my VHS-C tapes are SP, they seem to do fine in the JVC VCR. But you know more than me by far... so I was wondering why you would say that the AG-1980 is better for VHS-C tapes. I have another bunch of VHS-C tapes to transfer and so the question popped into my head.
VHS-C tapes are more fickle than a 13-year-old girl. JVC VCRs eat VHS-C tapes. Most VCRs love to eat VHS-C tapes. They tapes are made really shoddy, even the best ones from JVC. It's a piece of cheap plastic crap, with part of a VHS tape spooled onto the weenie little reel. No-name VHS tapes bought at a gas station near end-of-life of the format (circa 2000s) tended to be better quality mechanically than the best-made VHS-C tape.
Note that I DO NOT refer to the tape itself, but to the build quality of the cassette. Clearly a top-shelf tape will look and sound better than inferior no-name garbage.
One little slip or tug by the tape .... one slight imperfect in the alignment or build quality of the VCRs transport system .... and you can find 10 feet worth of film mangled and wrapped around every part of your VCR's internals.
Very often the adapters are to blame. Since you're using one of the best ones, the JVC-built powered adapter often sold with their higher-end S-VHS-C cameras, you've made one wise choice to protect the tapes.
I can't really explain -- in technical details -- why the Panasonic AG-1980P does better with the micro-format VHS tapes. It relates to the transport system, and just industrial tank-like quality of the unit in general. It's the only full-sized VCR that is allowed near VHS-C tapes, be it my personal ones or those of clients.
I've actually lost/mangled some of my own VHS-C and S-VHS-C tapes in various VCRs in the past. Even the cameras can handle tapes poorly if the tapes have been sitting for too long. Moreso than regular VHS tapes. I sometimes think the plastic cases used by those small tapes encourages tape death faster than cardboard sleeves -- moisture and humidity gets trapped by plastic, absorbed by paper. Tapes will "stick" when they start to degrade. And sticking causes jamming.
On an off-topic mention ....
.... I often wonder about DVD longevity, when stored in plastic cases. Between trapped air and chemicals of the case, it can't be good long-term. Paper has a downside, too, however. Nothing lasts forever, eh?