Steven,
Welcome to Comanche ownership and the ICS Forum.
I haven't had the exact problem you mention but did have similar issues with a very old DME, nearly original to the 1970 Twin. The internal part of the unit was fine but the connections had deteriorated over time as you described due to vibration and the heat of Texas on the plastic parts. I have to say it sounds a bit unusual that a connector cannot be replaced but then with older parts and retrofitting, that can happen.
If the IA says this is a Comanche part, the part number would be in the manual on this website at
http://www.comancheflyer.com/NS/index_serv_manuals.phpI've had some success at googling the Piper part number and finding the part.
Don't know if it would be helpful but the maintenance manual for the MX12 is downloadable from here
http://tkmradios.com/uploads/MX12_MAINT ... MPLETE.pdfI have found over time that IAs have varying skill levels on various topics. The shop I use regularly raises their hand on avionics issues and suggests I take the plane to an avionics shop. Can't tell if this is one of the situations or not.
Hope this is helpful and please share what happens so we can all learn. Thanks.