"Battery Is Not Charging"

I have a 2017 13-inch MacBook Pro, running Mojave 10.14.2, and I'm having a recurring problem with charging the battery. I bought the computer new about six months ago.

The problem is that I often get a "Battery Is Not Charging" message when plugged in to power. It doesn't happen all the time, and often corrects itself if I disconnect and reconnect. But then "Battery Is Not Charging" comes back, seemingly at random, which I usually don't notice until my laptop suddenly dies. I doesn't matter which of the ports I use, and I'm pretty sure it's not a physical issue with the charger.

I've tried resetting the SMC (which is everyone's first suggestion), and it does temporarily fix the problem. But within a few hours or days, the battery drops to zero while I'm plugged in, and I see that "Battery Not Charging" has returned. This issue hasn't rendered my MacBook unusable, because it does charge successfully most of the time, but it has made it unreliable and frustrating to use.

Any thoughts on how to address this, beyond resetting the SMC constantly?