Roboteq 2130 with Spektrum Loss of Control

I have a Roboteq SDC2130 with a Spektrum DSMX Model 9645 receiver and Spektrum DX8 transmitter for remote control. While I have been developing with a desktop setup, twice the Roboteq has unexpectedly started moving the motors without input from the remote control. Both times, I was running Roborun+. The second time, I happened to capture the spectrum inputs the roboteq was receiving (see below).

''Running out of control for 4-5 seconds:
?K 0
K=812:540:513:556:1023:54:556

'' Back in control
?K 0
K=342:682:629:0:646:682:556

I am using channels 3 and 5 for controlling the motors. As you can see, while the motors were running out of control, channel 5 was pegged at 1023. After regaining control, channel 5 is back to its center position of 646. I did not do anything to the transmitter to regain control. I am wondering what might have caused this and how to prevent it in the future. This is a very real safety concern for me.

Stephan