Different battery charging issue?

Hello everyone, my iPhone 5C that I have laying around has a strange battery issue that I've not seen before.

Firstly, when the battery runs below operating voltage and shuts off, the phone must have it's power button pressed until it shows the low battery symbol before it will begin charging. If I do not do this, it will not charge, no matter if I leave it plugged in for multiple days or weeks(I've tried this).

If I don't begin to charge it in time(<2 -3 days~), the voltage will fall too low to even show the low battery symbol when I hold the power button. Once this point has been reached, the phone ceases to charge at all. I then need to use an alternate 5C or 5S to charge the battery a little then transplant the slightly charged battery back, which will then continue to charge again.

I've tried multiple batteries, new and old, and also various chargers of different amps. I have also changed a few lower charge port assemblies from working phones to no avail.

Every battery that is too low to show the low battery, will not charge until I begin charging it in another phone.

When the phone is powered on, it will always charge as normal.

Is there an IC or resistor that could've been fried?

Thanks in advance,

R

EDIT: I've also tried reflowing the board with a hot air blower, no luck.