My '93 has that same wire problem. There is a plastic retainer in the plastic clip that holds the contact in. Mine is still in there but will let it slip passed if you're not careful. I'm able to just push mine on after attaching the plug and it holds fine. You could retention the contact to bite harder or just go to a junk yard and find a used connector end to replace the whole deal or just the plastic housing if your contacts are in good shape.
If the only problem is that the wires won't stay in the plastic shell, a hobby type hot glue gun with HI-temp hot glue is the fix. The smaller hot glue gun that uses /1/4" glue sticks is just the right size for the job.
Hot glue or epoxy would work. It's really not a major problem and easy to fix. Once it's nice and secure you're all good.