Martin,
Mismatched crystal could be your problem, because this effects tuning and thus range. One interesting point is that Horizon sells and advertises these third party receivers on the site as JR comatible. How can the same company tell you that the receivers work with JR, and then tell you that they may not. We have a conflict of interest here. You can't have it both ways. It goes back to the idea, that when you mix brands of equipment, you are responsible for the result of the mix.
Dave