I have an older 500A. After many years of use, the lugs on the trigger housing broke, causing the front of the trigger assembly to drop slightly out of the receiver. This happened three years ago. I ordered a new polymer Mossberg housing from Numrich. After disassembling the old parts from the original trigger assembly and installing them in the new housing, I made sure everything functioned properly with the shotgun. Since then, I have used the shotgun very little. The other day I was shooting trap and the lugs on the new trigger housing broke again. Could there be some reason for the lugs to break so soon after replacing the housing? Has anyone had experience with an all metal trigger assembly? If so, will it fit an older model 500A?