Park and Unior truing stands, as well as all of the copies there in, go out of dish in use. It happens faster than one might assume. One day you are cruising along, using a dish gauge just to double check the stand, and the next day you are building a wheel only to find it’s 2cm outta dish at the end, and your eggroll is soggy.
There are two ways to correct this, but only one sure fire way. The halfass way is to get a wheel that you think is in dish (if you have a dish gauge check it!) and stick it in the truing stand. Then follow the directions for recentering whatever stand you have, using the wheel as your calibration device. I say this only sorta works, cause it assumes a perfectly true and dished wheel.
Luckily Unior makes this truing stand calibration device. Stick this chunk of aluminum in the stand, tighten the truing stands axle holding arms, then ease off a quarter turn so the Unior tool swings free, but with no play at the axle clamp area.
Dial in your truing calipers, and assess which way you need to move the stand. Move the stand, retighten and check again. Sometimes it takes two goes. Very easy once you get the hang of it, and makes less work for you, re: dishing, down the road.