The wrong BLE channel calculation of iphone13 pro

I am using iphone13 pro to connect with nxp kw45(one BLE SOC chip) demo board as master, but found the KW45 side report 0x3E error(CONNECTION TIMEOUT), I record the log with Ellysis, which shows the BLE channel calculation is not right which lead to the error.

The hop increment is 8, channel map is 1-3, 6-33, 36, in Frame 45093, the channel number should be 9, not 8. connection interval is 30ms. My question is it normal, any advice? Note: This problem is sporadic, not easy to reproduce.