Hi
It looks in fact like it is a SAFC (0x37) strobe that is being sent. From the returned status byte is looks like the radio indicates that it is already in IDLE. (returned 0x0F).
If the radio was in RX when the "IDLE" strobe was sent, I would expect it to look like this:
Here a correct IDLE (0x36) strobe is sent and the radio returns the expected status byte when its in RX, 0x1F.
I would do a check in tha code by reading MARCSTATE or the SPI status butes that the radio is in fact in the states the expect it to be,rather to rely on current measurements. It seems that there might be an SPI issue here causing this behaviour.