[lkchris]

I haven't done mine yet, but this sounds very unusual.

The metal female connector should have a tab whose purpose is to keep the plastic insulator from coming off. There's really not enough size to this connector for a second pin or tab.

Perhaps the male spade on the filter was misinstalled between the plastic and the female connector rather than down the center of that connector and became fouled with the retaining tab.

Or perhaps the retaining tab had been bent into the center of the female connector.