UART / RF latency with 802.15.4 module (XBee Pro)

We are facing a strange behavior using XBEE 3 module (802.15.4 mode with fw ver 2006).
We send PPS synchronised messages from one XBEE module (@115200 bauds) and receive them with a measured latency about 40 ms between depending the case.
We are communicating in broadcast mode.
Could you tell me if such a latency is a “normal range” ?
It make me think about a abnormal “buffer latency” inside the XBEE module.

Thanks for your feedback.

No, that looks to be normal.