charging problems

For like the past year or so, my iPad Air 2 has experienced some charging issues, which have recently become worse. If I unplug my iPad and the battery drains some, and then I plug it in to charge, it has not been charging right away. For instance, I might watch a movie before going to bed...

Here's the setup: Sister-in-law has iPad Mini version 4 (latest model) iOS 10.3, loves it. After having it for 7 months, one night it won't charge. No slow degradation, no battery problems or fussiness with the port or cable. Just no "buzz buzz" when it's plugged in. Did all the usual "reset...