Dont worry about it. The Pb receivers are set to a higher sensitivity than Wea and with extra sensitive patch antennae and being close to the Tx there is probably some swamping.

I have noticed occasionally that my Wea receivers, paricularly those with patch antennae, give a slightly odd behaviour when the Tx was very close. Never a problem in flight, or even when moving the tx a couple of feet away.

I have just tried my Core with the 9 channel receiver. When the tx was within one foot or so of the Tx the RSSI and LQI values were all over the place. Moving to about three feet all was perfect,, RSSI S around 18 and LQI at 100 % .

Real world experience.