Many has changed since APM, you'll be surprised. Best thing to do is connect the AT to mission planner, select Antenna tracker from the drop down box in the upper right hand corner and look at the error messages you get.
"I can confirm the deviations in tracking, as well as delays, as well as pointing correctly if the plane moves from right to left and a big deviation when the plane moves from left to right. It makes it almost useless. Sorry to be so critical, but…"
"By the way, don't wait longer before doing the release. I test when a release comes out, I don't test beta stuff... I think it was perfectly ok to do the release. I hope you can find what went wrong."