RF woes

Anyone have any insight into why four separate 411a systems (blk
21/22) would all experience terrible range in a totally rf free area?

I had a shoot in northern Alberta (in the middle of nowhere) and was
using one block 21 and three block 22 411a systems with um400 trx's.
They were tuned correctly to avoid inter-mod (group A on blk 21 and
group B on blk 22). I must have done about 100 scans on the 411a's
and there was not even a blip of other rf on them. I have owned two
411's for about a year now and the settings on them were right so I
have ruled that out. My range was down to about 25meters with a clear
line of sight and fresh batteries on all four. I thought that it
might have been my 744t giving me issues as I have read other posts
about them emitting rf but even when it was powered off or completely
out of my bag it was the same. We were using the XD cam but I have
done shoots with the exact same camera and it was fine so I don't
think that was the problem (also, we were not using a video
transmitter). I could not figure it out to save my life and it drove
me totally nuts on a reality shoot where I was depending on the wires.

Thoughts?

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