I have observed this keenly.
When charging from below 20% SoC, it sometimes charges slowly.
But if you switch off the charger the switch it on again it charges fast. (Unplugging not necessary, which indicates no issue with usb ports)
This slow charging never happens when charging from above 20% SoC.
I guess its a bug, where the phone doesn’t ramp up charging as it should and instead charges with the default 5W as if the PD PPS handshake is not happening properly b/w the charger and phone.
Also in this case the phone gets hotter.( While it remains cool during fast charging)
Indicating perhaps that the phone’s onboard power converter is being used, instead of the charger’s as per the PPS protocol.
PS i use the Samsung 25 w PD charger.
When Working Properly, it charges my phone
@ approximately 2% per minute rate.
Which is very fast.
