Diagnosing 4G disappearance: where to begin?

Installing and Using OpenWrt Network and Wireless Configuration
1

Hello!

Setup:
Router/modem: PC Engines apu3
Firmware: OpenWrt 21.02.0 r16279-5cc0535800 / LuCI
4G module: Simcom SIM7600G-H LTE
DNS: 1.1.1.1

Every now and then(sometimes twice a day,
sometimes every few days, sometimes once a
Month) my internet stops working and the only
fix is to restart the router. There seems to be no
indication anywhere in Luci that anything is wrong.
The system log has no entries around the time
it stops working, the last being a DNS renewal
(at least the last time it happens).

I tried messing around with uqmi to get more info
but everything looks fine there: data is
"connected", IP address is assigned and the signal
is fine.

I ran a few utilities through Luci:

Ping:

ping: bad address 'openwrt.org'

Traceroute:

traceroute: bad address 'openwrt.org'

Nslookup:

;; connection timed out; no servers could be reached

The question: how do I go about diagnosing it?
I'm not sure where to even start... Qmi? Openwrt?
My 4G provider?

Sorry for the dumb formatting, seems the input box
cannot be scrolled on mobile...

2

DHCP renewal, I assume?

Try running a constant ping towards some IP on internet, like 8.8.8.8, see if it keeps your connection up.

3

As in from when I restart it to get it to work until it stops working?

Will do as it's easy to try it, but what's the reasoning?

The last time it disappeared I did have a YouTube video playing

4

See if cuts out because of inactivity, but I guess it doesn't, since it did, while your were playing YouTube.