I suspect the board to board connector on the motherboard had a dry joint and by applying presure on the back and front of the phone, just above the charging port, presses the connect joint down onto the motherboard and it charges. Only problem with this is a) the dry joint will heat up especially if you try to fast charge the phone because of the amps being put through the circuit and b) the joint will become increasingly worse until even pressing down on the phone won’t get around the problem For anyone else having the same problem, first change the charing port to rule out the USB connector and then if the same symptons persist, you probably need the BtB connector replacing or at least re-soldering, I personally would replace it so you have new charing port and a new BtB connector