Yaw Rotating after triggering "Guided" from AltHold with about 40degress

Hi all,

this morning, I did some test flights and everythig works as expected. With the last start, I got a (Safe) notice in Mission Planner HUD after Arming. Okay, I started in AltHold flew to position and changed flightmode from AltHold to Guided. Directly, the drone was rotating on yaw at about 40degrees. I switched back to AltHold, land and power off the drone. Powering the drone again, no critical message and I started in AltHold again but I had the same behavior when switched from AltHold to Guided. I didn’t changed any parameters. The first 5-6 flights was totally normally.

Any ideas for that behaviour? Thanks!!!