If your receiver gets any voltage drop it will lock you out for up to 13 seconds. I tested a bunch of Spektrum recievers and many would not re-establish a link after loosing the battery for a split second. Most 72 mghz receivers only take a fraction of a second to re-link, but the Spektrum's take much longer and in at leset one case 13 seconds. Most were around 2-3 seconds. Way too long for a recovery at low alt. To avoid this problem always use a dedicated receiver pack and make sure it's fully charged. Another problem is if you are running too many servos on your ESC, if it's an electric plane. The voltage can drop if you are running more than 4 servos and cause the same problem. The 6100 was recalled for this reason.