Horrible oscillations on pitch-axis


I’m totally new to ardupoilot and also planes. I build an airframe with v-tail configuration based on Mini Talon design concept. I flew it two times and have experienced heavy oscillations on pitch-axis in FBWA-flight mode. During these two flights I only tried to fly it in FBWA and never switched to manual mode. The oscillations are mostly very slow - around 1 sec time period. Also these oscillations occur only with strong wind, or exzessive rc input. With no rc input or just within slow turns oscillations do not appear or seems to be very low. I already tried to set CG noseheavy, but it didn’t affect the oscillations.
By now I didn’t try autotune, as I’m a bit scared if it goes totally wrong. Could such oscillations be caused by bad PID-settings? What I already saw before were high frequency oscillations which were said to be caused by bad PID-settings. But in my case oscillations are very slow and also affect the altitude of the plane. You can see these oscillations on height-curve. What about this PTCH_RATE_SMAX setting? What does it mean when is set it to a lower value? Could this help in my case? Also i heard there is a autotrim function in ardupilot, but i think it is only for manual mode.
I hope you can help me to solve this problem. I would be very grateful for it.

Here is the log as a .bin-file: https://www.dropbox.com/s/7l0opn4lmpmcsqu/2022-07-20%2021-38-51.bin?dl=0