I bought one when it first came out and had some teething problems. Basically it would freeze and I had difficulty programming the parameters. Checked a several things, but ended up return the control head to TruTrak and they replaced it. Second one worked better, no problem programming it, but also had freezing problems, which occurred irregularly. Had to switch the unit off then back on to reset (resetting the altimeter setting). It would freeze with or without the AP engaged. I feed the GPS signal from a Garmin 500 GPS through a GDL39 ADSB receiver--all hard wired. I don't know what the problem was ultimately, but it seems like some of the GPS signal information was not always complete, or maybe there was noise, but when that happened the unit would freeze up. Interesting, it would still hold a course, but no adjustments could be made, and the screen was frozen. Yes the AP control could be released. Sent it back again and TruTrak replaced it again. The third time was a charm, it has worked great since then (now for a year). TruTrak's customer service is outstanding! Notwithstanding my initial problems, I would highly recommend the unit.