With true vacuum operated locks there is ZERO chance of an electrical fire in the doors.
Now if your vacuum is leaking, you need to verify if it is in fact leaking from within the dash. If it is, then I'd be taking the car back to the shop that replaced your airbags. Have them repair this leak, that they may have possibly caused.
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72
'02 CLK320 Cabriolet - wifey's mid-life crisis
2012 VW Jetta Sportwagon TDI...at least its a diesel
Non illegitemae carborundum.