Looking back through the thread, there is no mention of guiding. If you're not guiding, the Dec axis should just be sitting there doing nothing, which allows/causes you to see Polar misalignment as drift in Dec (I used 'allows' because this is the basis for 'drift alignment' - turn off guiding and tweak az/al to minimize Dec drift).
I don't think that cone error will mimic polar alignment error. As long as the RA axis is correctly pointed at the NCP, I don't think it matters to tracking if the telescope is slightly off from the axis. Now, I am absolutely not an expert on the geometry of cone error effects, but I think they manifest more in errors in having a goto command land with the target centered. Do you have a way to independently check your Polemaster alignment result?
Meanwhile - is there any 'play' in your Dec axis? If you try to wiggle the telescope back and forth, is it solid? (just don't push so hard you cam the gears!)