You must keep the router bushing perfectly centered to the router bit/collet, or you must always keep your router oriented the same way with respect to the dovetail jig. This is true for any brand of dovetail jig that uses guide bushings in the router to guide it through the jig.
I put an arrow on the top of the base of the routers that I use for dovetailing and point this arrow toward the jig every time that I am cutting dovetails. This is so critical that I do both to make certain that my dovetails are cut correctly. I use DeWalt 618 routers and they come with a centering tool to center both router bases and bushings to the collets. These centering tools are also available for sale if your router didn't come with one. It consists of a precision ground shaft that fits in the collet and a plastic cone that fits tightly on the shaft. With the shaft inserted and tightened in the collet, you place the cone on it and press it into the hole of the base or bushing and hold it while you tighten the base mounting screws or the bushing nut. The bushing nut needs to be very tight, as a loose bushing will ruin your dovetail cutting accuracy.
When you change the bit depth to adjust for the tightness of your dovetails, make only very small changes to the dovetail bit height setting and then make test cuts to see if it is correct. Once you have it correct, measure the bit height to the router base with a precision caliper and record the measurement somewhere safe just case you ever need to make additional identical dovetails. If you have this measurement (in thousandths of an inch) you can remove and replace the bit and return to the exact setting, but be careful since a different bit of the same size may not use the same depth setting.
Charley