I have been having battery issues since the April 2018 update. Getting hot, drain in a few minutes, etc. Did all work arounds. Nothing and since a few days also this one. If it is on, it doesn’t charge as the need of the phone is higher than the speed of charging!
I hope the new Android version solves all this battery problems. Otherwise I will send the Phone, as I still have warranty. But that’s not a sustainable solution…
Definitely contact support!
Don’t wait, as the any damage might spread to other parts of the phone, e.g. being caused by the constand overheating etc. FP even could hold you accountable for that, as you did not contact them on time (though I don’t mean to say they would even consider this; it’s just my thinking to take everything into consideration and prepare for the worst case ).