Apple has it has affected a "limited number" of USB-C cables. Apple did not offer an estimate as to how many affected units reached customer hands, but a review of the accessory posted to the Apple Online Store last September appears to describe the problem:
This cable has gone from kinda working (getting my macbook to charge after 20 secs of trying) to having to fiddle with it for more than 5 minutes before it works. As of now, I have to manually hold the charge cable into the port as far as it will go before it registers and begins to charge. The moment I let go it stops charging again. Then, randomly, it will suddenly resume charging as usual. This is incredibly frustrating and time wasting.
The replacement process can be initiated at an Apple Store with a Genius Bar appointment, at an authorized reseller or online via Apple Support channels. The program runs through June 8, 2018 so you have a couple of years to get your cables swapped out.
The USB-C charge cable program is effective until June 8, 2018 so exchange them now!
Affected Cable:


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