Restart QMI Interface on connection loss and: Is Google messing with me?

Hello again everyone,

I have hit a snag in my OpenWrt journey. It's been a real nail-biter so far and I would appreciate hearing your thoughts again.
In my previous topic, I asked for help and successfully installed OpenWrt on my Zyxel LTE5398-M904. That has been my internet access point number 1 in my house ever since.

Recently, even before I sysupgraded to the newest snapshot version (a couple of days ago), it started acting up. By that I mean, the QMI interface loses the connection to my provider (O2 Germany, formerly Telefonica) without giving any indication as to why (no error message or anything). Restarting the QMI interface or rebooting the device always fixes it, even if you do it all within a minute.

That connection loss happens more than three times a day now, a month ago it never happened.

My first questions are:
What could be going on? Can I set the Interface to restart automatically once it loses its provider-provided public IP? (My solution to date has been a script that pings every 5 minutes and reboots the router on packet loss)

Now for the second part: Is Google messing with me?
And I ask that not in the slightest bit sarcastically.
Ever since the connection aborts started being annoying, a really weird phenomenon also started: Some YouTube videos became unavailible. I first thought "Well darn, that sort of thing happens". But then, as the amount of unavailible videos started to become ridiculous like two weeks later, I tried it through Mullvad VPN and what did I see? All the videos were back. I then used a VPN server in my home country, Germany and they were still availible, so it was not a region-lock thing.
And here's the real kicker: Using the same SIM card in my backup LTE router (An archer MR600) made the videos availible too.
What in the name of (insert cliche) is going on? Is Google messing with me because I pinged them with a single packet every five minutes? Why is the phenomenon only happening on my Zyxel, not the TP-Link Archer and on my phone, which uses a second SIM with the same mobile contract? (That is why I don't think it is the provider's fault)

As a cherry on top: Since I sysupgraded to the latest OpwnWrt snapshot, the QMI interface gives the error "SIM_ILEEGAL_STATE" on device reboot and does not connect. This can be fixed by restarting the interface.
Also for like five minutes, the videos were availible, before vanishing into oblivion once again.

Thank you for reading this monolith and thank you for your attention, I look forward to hearing your thoughts and finding a solution together.
Best regards,

P.S. Sorry if this is a duplicate in any way shape or form, but I did not find anything similar typing YouTube in the search bar.

P.P.S Another weird thing is that if I open the video through a VPN and then deactivate that VPN, I can buffer the entire video, even though that video is supposedly restricted or unavailible ( / newpipe)