You make me wonder if my 82 has it with the later type dash box?
I haven't even paid attention myself, I won't trust the stock vw system so I have an electric auber gage/sender in one oil filter housing port, and the other port goes to turbo.
My 85 engine gives fits as is right now with that hooked up so I had to take it off after trying another sender. Sometimes it would get pissed off and not quit until you turned the car off and back on.
82 jetta that is now parted out and gone also started giving fits after months of being ok. Also did the manual gage thing and numbers seemed to be well within spec. On its last ride home it was flashing and buzzing at me now that I think of it. Only thing at that time was the oil light going off constantly in the dash.
One of those things maybe? I have had good luck for whatever reason with gas gages and temp gages in mk1 and mk2 cars I have had thus far, but still run aftermarket digital gages.
Oil pressure system has flipped out on me before many times on multiple different chasis so I just have to ignore that system, so much so I don't hook them up.