Vidmir Said:
"liquid detected in connector lightning: I have a problem with my phone, it shows me a problem with the ligtning socket that is wet. The phone had no contact with water. When the charger is disconnected from the power supply, the message is displayed all the time"
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Providing a Screenshot:
Can you provide a screenshot of this message? This will allow everyone to see this message firsthand.
Go Here: Take a Screenshot or Screen Recording on iPhone - Apple Support
Important: Be certain to leave out personal formation by covering it with rectangles.
Condensation may be the Culprit:
Condensation may have gathered quite a bit. And, that can happen indoors - typically in lower floor levels - so, that may be what has happened here.