[SYMPTOMS I HAD] it would charge very slowly, if the screen is on, it would actually discharge. When the phone was off, it would slowly charge (i.e. >5 hours to full charge). and it would discharge very quickly (i.e. 1% per 2~3 mins). When the phone was off, it would charge sometimes and sometimes not. Figured that when the phone was off, you really are negating much of the software influences so this could be a hardware issue, however, wanted to make sure before going down the hardware route.
Did some research, searched the forums and searched some more.
I had tried 5 different chargers, 3 different USB cables and had bought a replacement battery.
1. Cleaned with thick paper - no change
2. Cleaned with thick paper & rubbing alcohol - no change
3. Cleared with Compressed gas - no change (on first charge, there was a change but then back to normal)
4. Attempted to clean with vacuum (with finer nozzle) - no change
5. Used charging apps from playstore - didn't show charging details - considered the port was faulty
6. Tried to find default references for charging as mentioned in one of the forums - unable to find it
7. Found a replacement USB port charger board and replaced it - working fine
So it could be the actual port is faulty. If you symptoms match, it could be time to take it into the service centre, restoring to stock first of course. The note I am using had slow charging for about 2 months prior to really slow charging.