Mobile network drains 70% of battery per hour in Android 12

• /e/ version: 1.6-s-20221201239247-dev-FP3
• Device model(s): Fairphone 3
• Device rooted: no

I just picked my phone up after a quite while (a few hours) of not using it, and noticed it wasn't turned on anymore (I hadn't shut it down). After re-booting, I noticed EXTREME battery drain.

At 2:37 the battery was at 90% (ninety).

At 2:58 it was at 58% (fifty-eight).

That means, within 19 minutes, the battery lost 32%, which is insane. That means, it loses ca. 1.7% every single minute!

I did not do anything unusual, only one or two apps were running in the foreground, nothing was being downloaded, the device was inside at room temperature (ca. 20°C = 68°F).

According to the battery settings, the mobile network connection is responsible for draining nearly 70% of the battery. Though, the cellular data connection (a.k.a. 4G) has been disabled since the re-boot, and the device was only been connected to my WiFi.