Why does my central receive 2 rcv events for each received transmission?

Hello yet again Nordic World

And yet more WTHIGO questions:

10040 board as central under SDK 12.3.  For each message passed from a connected peripheral, the central board receives 2 rx events. 

Is this normal?

Are there classes of rcv events I can filter on?

If so, what are they and how can they be filtered?

Undying gratitude.

Robin @ TL 

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