If it stopped for an error, it should have started blinking a code on the controller. But the next time you press the extend/retract button it will clear the code so you have to look before you press the button again. I do not think there is a code for motors out of sync, I think it is mostly wiring or other issues. They have some good troubleshooting docs on the lippert website, which mostly relate to the error code, but might be helpful to browse.
Right now mine give a code for a ground to short, and that happens every time I turn power off and back on. So you could try that and see if an error comes up even though it went in. Either plug it into shore power or turn the house switch on. If it doesn't come up with an error you can try turning power off and back on a second time. I found mine only shows the error again after I clear it if I turn the power off and back on a second time. It was in the shop and I thought they fixed it because it didn't do it when I picked it up, then when I got home and plugged it in it was doing it again. So I found I have to take power and apply power twice. Is pretty odd. But waiting to get it back in there now.