This problem is seen on dual SIM and eSIM models.
The source found an unpleasant feature of the Apple iPhone 11. If the device works with two SIM cards, it spontaneously disconnects from LTE after a period of inactivity.
The problem disappears if you turn off dual SIM mode and use only one phone number. The check also showed that there is a problem in the iPhone 11 Pro Max for the Chinese market with two physical slots for SIM cards and in the iPhone 11 Pro Max with eSIM. Neither full recovery nor resetting network settings helps to fix it.
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