It's quite a simple thing, relying purely on
vacuum generated by a bellow in the dash, to pull up
oil through the hollow dipstick, thereby giving an indication on the gauge.
There's the bellow, and there's a short rubber tube between it and
the gauge, and then the other side of the gauge connects to the
plastic pipe from the dipstick.
Faults are most likely to be dash-located, and probably it's the rubber bits that have split.
Or a break/kink in the plastic tube somewhere.
N