Higher BER when adding both uplink and downlink symbols to a frame

[asedlmayr]

This only happens in hardware mode (-DUSE_ARGOS=true)

While testing with dl-powder.json, I 3 U symbols (2 of them pilots) before the "D" symbols (after the pilots and before the Downlink). The uplink symbols reported an acceptable BER but the downlink did not. I reversed the order (D before U) and noticed the high BER was only reported for the symbols at the end of the frame.

More testing required for better characterization of the issue.