can't turn off AP mode with RPi4

[yannig]

Hello Tim

thank you for your response !

I tried to update the kernel (to 4.19.97-v7l+ #1293), and at first, I seems to work.
But from the moment I moved the Rpi away from the router, the wifi connection stopped to work, even when I put again the Rpi close to the router.
(the raspberry Pi 3B wifi quality is : 63%, level -66 dBm at around 6 meters)

Now, each time I reboot the Rpi4B, it switches to AP mode, even with the RPi4B very close to the router !
(ethernet connection works).

I don't know what to try now...