Precision landing init failed

ArduCopter
1

I tested the precision landing mavlink command in SITL, but the AP always responded “PrecLand: Init Failed”, sometimes, AP responded “PrecLand: Target Found”, then it working well. But the message “PrecLand Init Failed” still appears frequently, and then the drone stop moving, Until the Message “PrecLand: Init Complete” appears. I send LANDING_TARGET message approximately every 100ms.

I want to know what caused that “PrecLand: Init Failed” error, did I send the message too slowly or too fast? Thanks!

2

And all I want to know is: How did the “PrecLand: Init Failed” message come about, and how can I prevent it?
Sincerely hope to wait for everyone’s help, thank you！