Limited range check can be caused by a number of things.

We suggest unplugging all but one servo and trying it again. In many instances it is a servo causing the limited range.

Also, if the range test was in a confined area such as on a street or parking lot, you're going to get bad results because in low-power mode, other nearby obstructions can cause issue.

Because you say you're getting reduced range at other angles, I would suggest moving one of the antennas as well. From batteries to wing joiners, esc's to power cables, you could be seeing some 'signal blockage' from obstructions in the plane.

-Mike