Glitching and unnormal yaw in the follower copter when using swarm option

i set up a leader and a follower as it is in the MP documents, first the follower copter arm, take off and hover by the MP from the swarm window then leader is armed by the rc and take off. as i click on the start button in the swarm window, the follower copter behaves very bad, glitching and make yaw although it keeps the offset distances but with a noticeable error like 2 to 3 meters. why this happens?

Don’t set FOLL_YAW_BEHAVE to 3.

Please post the log file from the follower vehicle.

The foll params was disabled. In swarm it is not enabled, only in “follow the leader” or “follow me” they are enabled. But I also tested them, and set the foll yaw behavior to 0 that is do nothing.