iPad Air turns off when not plugged in

I’ve had this unit for two years and it worked perfectly up until this July. At first it didn’t want to charge, so I changed the cable. Then it charged very very slowly and started dropping the charge extremely quickly, like 5% every 30 seconds. Did a hard reset, checked everything (no new apps or weird processes as far as I can see), trolled the forums - nothing.

Then it started dropping charge like crazy. I’d unplug it at 100% and 10 minutes later it would shut down without even a battery warning. I plug it in, it shows me low battery and when it turns on again battery is at 40%, 5 seconds later it’s up at 80% etc.

Today I unplugged it at 100% and it shut down on me at 98% after 2 minutes, again claiming low battery and being at 80% when turned on again when charging.

I am now literally chained to the charger if I want to use the iPad and it’s honestly abysmal that there’s no solution for what I assume is an update bug (and apparently not the first one of its kind). The update has been out for at least a month - is Apple doing ANYTHING to make this work? I have not paid good money for a device to be broken and not fixed by the actual company that made it.