When I was plumbing in my B50, I found some great info on the TE. line under the 'good practices/pneumatic' paragraph. I thought it may be applicable here.
http://www.borgeltinstruments.com/B50man.pdf

Text of paragraph follows:
The most common mistake in variometer installations is to connect two vario systems to one Total Energy line with a T-piece at the instrument panel. The only time that this is permissible is when both instruments are of the pressure transducer type. That is no flasks hence no flow. Flow sensor type instruments cause significant flows in the line to the T.E. probe and these flows can cause these instruments to interact with each other or with a pressure transducer type variometer causing weird behaviour or a general slowing of the response of both instruments connected to the T.E. probe.

The T-piece in the T.E. line should be as close as possible to the T.E. probe although in practice it has been found that if the T.E. line is split under the pilot's seat, further aft behind the seat or near the trailing edge of the wing no problems will result.
end quoted txt

It may be a cause....
~Travis
N4067U