Tio Pedro wrote:

I agree. But, one thing that should be proven is that both modules
are working as intended. The one being used for the remote
application *could* be defective. Swap modules and see if the
receiving problem also switches locations, or remains the
same.

The OP said that he did that, and the problem remained. It's certainly a
desensing problem due to local interference at one end. That's the only
possible cause.