I installed a snapshot for my Raspberry Pi 4 and my Alfa AWUS036ACM (MediaTek MT7612U) and I get this a lot (causes my AP to die):
Fri May 15 02:42:08 2020 daemon.notice netifd: radio1 (2733): WARNING (wireless_add_process): executable path /usr/sbin/wpad does not match process path (/proc/exe) Fri May 15 02:42:08 2020 daemon.notice netifd: radio1 (2733): Command failed: Invalid argument
I found this but my problem is not channel related.
It does work (sometimes for days) but then something causes this error and I have to remove the dongle and restart the device from Luci.
The previous version (April never did this).