If it's not already understood, I have had a great deal of trouble with WPC games with burned or "bronzed" connectors.
This does affect the power delivered to the Fliptronics board.
It *will* contribute to weak flippers.
Pull the connectors, examine them carefully. Even if the plastics look good, look at the 'pins' - if they're not shiny, replace the connector.
I still use IDC connectors as they're simple and fast to do with the right tool.
I get new IDC connectors from Mouser, haven't checked GPE but I wouldn't be surprised if they were available from there or several other choices.
When ordering new IDC connectors, be sure it's rated for the right wire gauge size - save yourself some frustration.