Chosen Solution

i’ve assesed a clients phone and the charging jack is okay, but the phone still has a problem charging..where should i look?

You should check the connections from the Socket Charging to the C - Power Bauur inside the device and your money using a device called Avoometer

You can replace the charging socket witch is probably damaged unfortunately ifixit doesn’t have a guyed for it so look on YouTube for a guyed and i would say to go to eBay for the part

After one hour and it charge one

To take a look on battery terminal if a well connected second to check life of battery

Take a carefully look at the battery terminals if we’ll connected, you can as well try boosting the battery if situation persist try replacing the battery. More technical you can run a jumper from the positive terminal of the charging legs to the vbat.