Hi!. I have a problem with my iPhone 11 Pro Max. My iphone has 100% battery condition on the iOS 13.3.1 software and I noticed that when the phone is charged to these 20-40%, the battery often drops by 2%, i.e. the phone lies a few minutes at 30% and usually drops after one or at all. A 4 minutes later it can drop to these 28% and so again in a while . Yesterday the same thing, the phone had 73% or 72% watching YouTube, I look after 4-5 minutes and has 70% .. What could it be the fault, software or hardware issue? Update or battery calibration can fix this? The phone is not used much by me. Anyone had the same thing? It is troublesome, it happens most often after turning off the screen and turning it on again. Sorry for my English, I hope you'll understand this.