Clearly, the diaphram has a defect in it. This hole is excessively large for the amount and quality of vacuum normally available from the car's system to act on the diaphram sufficient to move the deadbolt. Perhaps if you apply more of a harder vacuum to the vacuum line running to the deadbolt you will be able to establish enough of a gradient across the diaphram to move the deadbolt.
One suggestion I have is to find someone in the HVAC business kind enough to indulge this sort of experimenting. HVAC people use vacuum pumps capable of pulling a reasonably hard vacuum (several Torr) at a flow rate of several liters per minute. Perhaps this would displace enough air from the vacuum side of the diaphram to move the deadbolt. Good luck.