I think a lot of this can be traced to the simple act of "reseating" the connector when you install the daughter board. That action alone, without the daughter board, would temporarily buy you some time and "fix" your reset issues for a month or??
I recently started having reset issues with our WCS so, finally having a machine to test these on, I bought a standard and a pro (by the way, amazing shipping, ordered Saturday morning, in hand Monday afternoon.) Before I installed it I followed "the steps" to pinpoint where the issue was in my game, measuring all voltage drops between connectors (where the issue usually occurs) Simply plugging and unplugging J120 raised the voltage sufficiently to make the game stop resetting (from immediately when both flippers pressed to not at all after three or four games.) I still installed the Pro to monitor the LED. Played a few more games and it stayed green. No doubt replacing the header and IDC connector is the final fix but I still want to monitor this LED to see how long reseating connectors helps.