Throttle stop after front transition

I got a full vtol mission flight, all goes well except that, after transition to fw, my plane suffered a height drop about 3 meter(not fatal, but confusing!)
I checked my log, it shows that, the pusher throttle has a sudden drop after transition is done! My transition speed is set as 18m/s and Iโ€™m sure the motor is good enough for that.
here is my flight report
https://logs.px4.io/plot_app?log=f10ed9d8-4eab-4b31-962f-bd5c69178878

and I checked source code, and I found one function might be related to this problem:

For future reference, hereโ€™s the corresponding Github issue. https://github.com/PX4/Firmware/issues/8508