Always plugged in ipad stops charing...

In the UK - We are using two iPads for our till system - a gen 1 iPad Pro, and an iPad mini.

Both are plugged into 2x separate wall outlets - and 2x separate 20w usb chargers and use genuine apple 1m lightning cables.

They seem to be fine for about a week - then we start getting “not charging” messages (green battery still showing), and the battery level starts dropping. As low as 45% we’ve seen it go.

Sometimes they charge again, sometimes we have to pull cable out to make it charge again.

We’ve tried changing the cables/chargers - we are now considering changing the wall outlets.

can anyone offer any advice?

many thanks.