Namco coin acceptor is a butthead

[legoman]

Hey gang, this has been driving me nuts for a couple weeks so I thought I'd see if you have any advice.  I have a Namco Mario Kart Arcade GP2 cabinet (very cool game, by the way, you can race as a Tamagotchi?) whose coin acceptor was disabled at some point.  I'd like to set it on coin play, but I get the feeling something's missing.  I can get it to coin up just fine in JAMMA test mode so I know I have the correct wires, but in actual game mode it will only coin up intermittently, almost at random.  From my research I figure it either has something to to with a JVS converter or possibly the brand of coin mech called a MEI Cashflow.  I bought a Cashflow just in case, but I feel like it's a dead end.  Anyone ever had this sort of problem with a Namco cabinet before?  Sounds like it can happen with Naomi cabinets too, but I've never read about anyone finding a solution.

[legoman]

Or, this is more general, do you know any way to artificially lengthen a button press?  I could wire the service button to the coin switch, but the button press from a coin flying through there isn't long enough to register a service credit.  Resistors maybe?