[Solved] What is wrong with pin 8 on LN822HKI, when trying to use it as rel_n?

I try to connect a small 3.3 V buzzer to my smart plug with LN822HKI controller in.
I created a small 5 mm x 5 mm board with an AO3401 Mosfet and 47 k resistor across Gate and Source. The buzzer hangs between Drain and GND.
I connected this board to those pins:

A8, 3.3 V and GND.
After evaluation of the board, there should be sufficient current for the mini buzzer (28 mA), as the AMS1117 3.3 V with BP2525D before, have enough headroom.
No problem defining pin 8 as rel_n, but as soon as I connect my small board, the application freezes and is no longer reachable via WLAN.
Its no current problem, as I measure stable 3.312 V, which looks even quiet clean on an osci.
Testing the board standalone works perfect: connecting to a 3.3 V source and connecting Gate to GND, the buzzer does its job.
So I have learned that pin 9 left of pin 8 bring the board down for flashing, but I have not read similar things over pin 8.
I can toggle Pin8 without connected buzzer, as soon as I have defined it. The only problem is that once I connect the mini board, the application freezes and does not boot on repowering.
Here are some more pictures of the UPXNBOR-XT03:



And the pictures of my buzzer installation:



So the question is: Has pin 8 a similar function like pin 9, that freezes the µC?

Added after 13 [minutes]:

Just to explain the buzzer:
The buzzer should sound when a device plugged in is running for longer than configured, and if it is running outside of business hours. Just an acoustic reminder, before silent shutdown after a period of rest.

Have you checked the LN882H datasheet?

I'm pretty sure A8 and A9 are both bootstraps.

Both are Bootstraps.

Thanks for forcing me to look again. I was somehow under the impression that it can also be not true, as triggering A8 once it is configured as rel_n has not stopped the board. So perhaps this pin can't even be toggled.
Now I moved one pin to the right, using A4, and my beeper sounds!
Thanks again for this needed bump!

BTW Is there something more available, as this small datasheet, with real information about all components, etc.?

It might help to read the entire topic.
https://www.elektroda.com/news/news4027545.html

Using pin A4