Reading this I went and double checked my Vintera 70's tele bass.
I never noticed any issues with the tone or volume pots on mine. Not as responsive as a split - P for sure, but I get what I would expect in variations in volume/tone using the knobs. It's a fairly dark pickup for sure, but has a mellow bite when fully open.
Hope you get yours sorted.
I'm a big fan of these Mexican basses. I have four now A flea, Player plus, the 70's Tele and just picked up the Vintera ii 60's P. I can't knock any of them for craftsmanship, fit and finish. In some cases better than some American versions.
I have had to do my own tweaks to get them how I like them, basic stuff, truss rod, string height and intonation, but after that I have been happy with them.
People complain about the high prices on these and I agree somewhat, but hasn't everything sky-rocketed in price lately?
I still think you get a good bass for your money in these middle tier Mexican range.