Define "lift all the time" for me. I had a vario that when on the
ground was showing slightly up all the time. This (winter?)
mechanical vario doesn't have any adjustments available. I was told
that the paint on the needle looses a slight amount of mass over
time. The fix was applying a very small amount of clear nail polish
to the needle until it settled down to zero. Took a few dabs to do
but fixed the issue.

On the leak test idea from Ralph - Interesting but I don't quite get
it so let's see if we can add some more details. There are three
possible culprits of leakage. 1) The tubing (from tail to vario and
from vario to bottle). 2) The vario (often at the face plate). 3)
the bottle. Now to test. So I have a U shaped tube with some water
in it. Disconnect the TE probe. Attach the U shaped water tube to
the female TE probe's connection on the ship (typically at the
rudder). Be very careful not to allow water into the ship's tubing
going back to the vario for obvious reasons. At this point one end of
the U tube is open to the air (true?) and the other end is aimed back
at the vario/bottle. Then create some slight positive pressure on the
system (ship's tubing to vario to capacity bottle) by lowering the
open end. I would think that the open end would need to be sealed to
create this pressure. Because the ship's tubing and vario is a sealed
system (we assume), the water in the tube will not be level. Mark the
current water levels. Then check back in an hour. If the two levels
haven't changed, then the tubing+vario+bottle are leak free. If the
levels have changed (become level over time) then you have a problem
somethere in the system. To determine which part is leaking you need
to do a process of elimination by performing the same test at the
vario and then at the bottle.

Thanks, John DeRosa