Do some VCRs crush blacks internally?
 

I've been comparing captures from a Panasonic PV V402 and PV VS4821. While the latter is an S-VHS that's probably not regarded too highly I've noticed that it's clipping blacks no matter what I do. Would a proc amp save this, or do some VCR's just clip levels during their internal processing?

Low-end VCRs -- mostly 00s decks, some late 90s -- simply overprocess video. It's the same reason that stores like Best Buy pump up the contrast on TVs. Too many consumer want video that is hyper contrasted, and "colorful", even if it truly damages the output quality.

Both of those are notorious low-end Panasonics. Nothing special, nothing good.