Problem of demodulation

Hi:

Lately, I encountered a problem with tx/rv packets by using tunnel.py
script. In 2.4GHz band, there are two nodes trying to ping with each
other. GNUradio node A can receive ping message but the node B can’t. So
I check the rx-power-log and see the power level of both nodes have
similar strength. However, when I check the demodulation log file, node
B cannot demodulate the message correctly cause most of the signal are
below some threshold. Does anyone know why node B cannot demodulate the
packets correctly?

The weird thing is when I use another node C to transmit packet to node
B, B can be pinged successfully by C. So I guess the hardware of node B
and the script should be normal but don’t know what happen.

Any suggestions will be appreciated!
Thanks!
KC