I've got the first japanese version of Esprade (4/14) today and tested it. Unfortunaly, I've noticed an issue. When there is too much action on the screen, the bottom part of it start to blink badly. During a boss battle, the top part of the screen start to blink as well.
I've owned an internationnal version of this game and I don't remember about such an issue. Does anyone have the 4/14 version ? Does the 2nd version (4/21) correct this bug ?
I have the international version (don't know which date, to lazy to boot it up), but mine does the same thing. Its just the hardware being pushed to the max and not anything wrong with the PCB.
All Esprade PCBs I've ever played had the flicker, as Dave said it's an issue of the hardware. The flicker will not appear in MAME, because of the more powerful CPU, maybe that's what you are remembering.
DoDonPachi (not DonPachi) has the flashing sprites problem at times like when 2nd boss explodes. Sometimes even your ship disappears during the explosion.