Cell phone didn't charge overnight

I plugged in my phone last night to charge. For some reason, I had 33% battery power this morning.

I don't know whether the USB cable is acting up or if my phone had overheated while I was asleep. Weird.

Luckily, I didn't have to go anywhere today, so it continued to charge at home. I typically don't go out on Sundays, so it all worked out nicely.