I think the owner has even more, I just have four of them to deal with for now. All had leaked capacitors and, except for one, would not turn on at all until the capacitors were replaced. Now they turn on, but with wobbling screens/low voltage.
I haven’t replaced the TDA4605. Have you?
Since it is the controller for the main switching MOSFET QP2, it seems to me that all these TDA4605s could be faulty. Maybe the replacement of diodes DP3/4, optocoupler, QP2, small capacitors etc. just helps the faulty TDA4605 to limp along for a bit longer.
I had another suggestion for the one component that I think is supposed to be temperature-sensitive: RP2 at the power input. The schematic says ‘20 ohm cold’ and I think this resistance is supposed to increase as it warms up - isn’t it intended to give a little jumpstart to the regulation circuit, to avoid the chicken-and-egg situation of no output to regulate? I wonder if that part is faulty, perhaps the jumpstart remains for too long and interferes with the output.