Just buy a new board!

HECK YEAH!!!
Oh, wait, I no longer sell those boards... um... nevermind.

Seriously, though -- those 3A rectifiers could cause your issue but you said the +5V was working fine. That says the 3A rectifiers were fine. Bad solder joints can do amazing things, though.

Do make sure you are measuring the +4 and +8V while using the digital ground and not the high voltage ground.

Yep, there's your problem.
Pin 5 of J3 is your high voltage ground, pins 4 & 5 of J2 are your low voltage (digital) ground.
Use the negative end of your 3300uF cap to measure this voltage.

Nobody knows why Gottlieb isolated the two grounds. Using the wrong ground for your meter's reference is known to cause voltage to measure incorrectly even though they are working.

That 4 and 8V using the 'other' ground catches a lot of people off guard. All the others look to have been measured properly. I'm surprised none of the FB guys mentioned this.

If you look at the schematics - you will see there are two separate grounds on that board.
Nothing will happen if you tie the two grounds together. In fact, most (if not all) of the replacement boards have the two grounds purposely tied together to avoid this type of problem.