Hi, I checked your device now and I see a couple of issues.
Firstly the WiFi connection profiles are duplicated for some unknown reason to me:
root@d9858b6:/etc/NetworkManager/system-connections# ls -al
total 7
drwxr-xr-x 2 root root 1024 May 5 00:32 .
drwxr-xr-x 7 root root 1024 Mar 9 2018 ..
-rw------- 1 root root 339 May 5 00:32 balena-hotspot
-rw------- 1 root root 339 May 5 00:32 balena-hotspot.nmconnection
-rw------- 1 root root 166 May 5 00:32 cellular
-rw------- 1 root root 232 May 5 00:32 rhlh-wifi
-rw------- 1 root root 232 May 5 00:32 rhlh-wifi.nmconnection
See how there is a rhlh-wifi and a rhlh-wifi.nmconnection files with the same content. And then there are two balena-wifi profiles listed by NetworkManager:
root@d9858b6:/etc/NetworkManager/system-connections# nmcli c
NAME UUID TYPE DEVICE
Wired connection 1 b9630612-f9f5-3cb6-af01-5f2de3681894 ethernet eth0
balena-wifi 8c275c4d-6236-3ec2-89b6-66b0bb3ab4d2 wifi wlan1
balena-wifi c32b5cec-34cd-3163-ae0f-36efc76067c9 wifi wlp1s0u1u3
supervisor0 3934805a-2b38-4205-ae2e-d4d71bf2b6fd bridge supervisor0
QVNTRA 714d42f9-629b-4e94-b2c7-62a87fcf445f wifi --
cellular d811a35a-70fc-3716-84e1-a3578d10cc1e gsm --
That explains why the two interfaces are connected to the same network.
The second issue is that the rhlh-wifi connection profile does not bind to specific interface name as the other one does: the balena-hotspot contains interface-name=wlp1s0u1u3, but rhlh-wifi does not.
There an issue with that though as the primary interface may appear as wlan0 or wlan1. Currently it is wlan1. This is because the AP dongle was enumerated initially as wlan0 and then renamed to wlan1 by the kernel:
root@d9858b6:/etc/NetworkManager/system-connections# dmesg|grep wlan0
[ 9.720545] rt2800usb 1-1.3:1.0 wlp1s0u1u3: renamed from wlan0
To solve all of this I would suggest having two rhlh-wifi connection profiles - rhlh-wifi-wlan0 and rhlh-wifi-wlan1. One that binds to wlan0 and one that binds to wlan1. The rest of the content could be the same. This way you will have all of the connection profiles bound to particular interface names and this type of issue would no longer occur.
Please let me know if you have any questions.
Thanks,
Zahari