Header Disabled
Why?
And how did you get to 222 ms? If that’s 25 bytes application payload (plus 13 bytes for the LoRaWAN header, so a total of 38 bytes), then the time-on-air for SF9 is 267 ms. Or, if it’s 25 bytes total, so 12 bytes of application payload, then 206 ms.
Also beware that nodes might have a random delay before they truly start sending? At least, the specifications state, emphasis mine:
2.1 LoRaWAN Classes
…
The transmission slot scheduled by the end-device is based on its own communication needs with a small variation based on a random time basis (ALOHA-type of protocol).
Finally, note that LoRaWAN explicitly defines when to expect a possible downlink (see RECEIVE_DELAY1 and RECEIVE_DELAY2), so listening after 500 ms is too soon for LoRaWAN.