There were a number of people posting in forums about this back in 2014 or so. Apple even went so far as to contact folks and ask them to send the cables in for analysis. As far as I know, the consensus was that perhaps the port contact spring was failing to maintain a good connection.

I don't know what the current status is but it doesn't seem to be an inherent design issue, except for the fact that the port has the springy bits and isn't easily replaced.