Eufy indoor cam stops recording without internet

I have set up a 2k indoor cam to record events on the local 32gb sd card, but it fails to do that after few days without internet connection

There is no wifi so I use a mobile hotspot on my phone whenever I want to access the camera over the eufy security app. I’d like the camera to work offline the rest of the time.

For 2-3 days the events with human detection are recorded autonomously (while offline), afterwards this suddenly stops and just shows the pulsing blue led circle (indicates “ready for setup”).
The only thing required are a few seconds of connection to the mobile hotspot. Then I can disable the hotspot again. No need to open the eufy security app or anything. The camera works for the next days, until the led starts pulsing again.

What does the camera need from the internet? Any way to fix this? I can’t use this camera if it requires internet all the time. Thanks for your help!

The continuous rtsp video stream could work, but that requires a second device to record the footage 24/7.
I’d prefer to record only the events with human detection, but I need help to get this to work offline.