Probably not a rig tuning issue but rather a hydrodynamic anomaly with
your paddlewheel.

If the paddlewheel is mounted off of the boat's centerline it will
rotate differently on on tack than the other and 1. differing depths
(on one tack the paddlewheel is deeper than on the opposite tack. 2.
the amount of leeways 'slip' the boat is experiencing versus #1
above.

Unless the paddlewheel is accurately mounted ON the boats centerline
it will virtually ALWAYS read differently when SAILING on different
tacks. Its a problem of hydrodynamics versus different 'flow
regimes'.