Did a re set and the problem the same suspect its the headphones socket itself when you wobble it it seems to work then not and then both work internal speaker and headphones .
Given up and moved onto Bluetooth headphones which work well and connection is good gone for the Onkyo E200 BT . headphones supplied are totally useless and adaptor and sockets worked for a limited time .so the headphones socket become totally useless now .
Any one else struggling with headphones don't waste your money in corded the quality poor and they don't last .
Get a Bluetooth pair