Ron, I am having two visions that might be the answer to your glitching. My first vision is the one I would check first because I think it is the obvious answer. Bare with me since I'm new on the block and you may have been told this already but electronics is my field of work... I think there is something wrong with your antenna itself at the solder point in the receiver. You say it does intermittent crap when it hangs free yet it is solid when it is made immobile. Something is failing when the antenna moves. Either it is slightly loose at the solder point, or it is a cold solder (which can appear to be just fine), or the solder pad on the circuit board is cracked or otherwise failing to make contact. The same could be but, in your battery connections, if they are loose or dirty at all it can also raise resistance in the battery. Put a meter on the antenna tip and where it solders to the receiver and check continuity while wiggling the antenna wire. I would check from one end of the antenna to the other since there could even be a break somewhere in the insulation which could be anywhere along the length of the wire. A shortened antenna would work for a fair distance before getting glitchy.
The other way to clean up what you think might be external RF interference is to wrap any power and glitching channel wires through toroidal ferrites. It's essentially a small tube made of ferrite. You wrap the wire as many times as is possible around one side of the tube and plug it into the receiver as usual. The coil you make from turning the wires through the tubes is known as a choke and will quite literally "choke" any RF from being able to pass through the wires! It's an easy and cheap fix. I find these ferrites in junk electronics all the time and they are used in computer monitors extensively for another free source. You obviously want ferrites that are big enough to pass the plugs through and small enough to keep from adding too much weight. I've seen these chokes protecting wiring in $10k planes!
I hope this helps at all. Intermittant electronic problems can be a nightmare. I've seen components fails because they were a little too hot or too cold! Plus these parts are getting smaller just as I'm getting older and blinder! That really helps!
Hope you find it, just remember to recreate the conditions while checking the circuits and you'll likely find what's wrong. I hope so at least!
Good luck!
Blisster