iPhone XR sometimes doesn't recognize charging cable.

My friend's aging mother has an iPhone XR that behaves strangely. Sometimes it fails to recognize a charge cable and sometimes it mysteriously discharges in a short time even though not being used. Sometimes it holds it's charge well. The Settings > Battery Battery Health reports that the battery is at 94%. The phone has been used very little. My best guess is that there is some contamination in the socket or that it was damaged. If so can they be repaired? Are there other possibilities?