I have been flying my NexStar and have not had any problems - related to the plane that is . One of the gear legs came out when I was testing it - pulling it by hand - but it was just a matter of pushing it back in all the way. The right thrust was perfect, flys beautifully - according to all of my instructors that have flown it and lands great. I did have a problem with the straight tracking while taxiing but it was just a matter of working on the nose gear and getting it straight. It is touchy to get it straight but maybe that is one of the 'every plane has it's querks' examples. After a few tries it is perfect.
Good idea about one of the gear sticking, that definitely could be a cause.
Oh yeah, I have heard a lot about getting a different trainer because of taking off the 'trainer' stuff that came with the NexStar - this was also recommended by the instructors at my field. I have never used the AFS (AutoFlight System) but did with the others for a bit. It takes some trimming but was good for my first few flights. I removed them one at a time and now fly without them.
As others have said, there are better and cheaper ones out there, but I am satisfied with mine.

Preflight - Preflight - Preflight