Frame output faults are just about the No.1 most common fault in all TV's. Actually, my own TV is a Mitsubishi which I believe uses a similar circuit to yours.
Basically, the frame output IC dissipates a fair amount of energy as heat (it's on a heat-sink). Several capacitors are fitted in that circuit to control the characteristics of the amp.
Components, especially capacitors tend to change value as they age and due to heat. If the capacitors don't operate as intended the IC will run even less efficiently and dissipate even more power. It's vicious circle & the end result is crystallized connections & breakdown of the soldered joints.
When you thwack your TV, you make or break the poor connection(s). Although you still have your aged capacitors to replace to get the frame amp. to run correctly again.
Capacitors are fairly cheap. I would normally replace the frame IC along with the poor capacitors (as it will have suffered somewhat) and resolder the bad connections for a reliable repair.
Cobweb
June 2005