Your Tx sweeps look OK but your Rx sweeps show no Rx, nothing but noise.
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I'd check the inductors and transformers used by the Rx, the BPF and the trifilar transformer. Bad connections here could be the problem.
Another thing to try is to turn it on with no USB cable connected and listen to the FT8 signal.? Does it stop after 45 seconds?? If it doesn't that may be an indication that something is wrong in the USB cable region, although it's difficult to say RFI if you aren't transmitting.
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All speculation but may help,
Chris, G5CTH.
