The DuMoulin Mauser has a 3-position swing-type safety (think Model 70), it retracts the firing pin, lifting the striker sear from the secondary sear when the safety is applied, allowing the secondary sear to lift off of the primary sear (trigger nose). When the safety is pushed forward to the fire position, the firing pin is eased back down onto the secondary sear. Since you changed out the trigger and the new trigger's sear is farther to the rear, you need to work on the striker sear to ensure it actually lifts off the sear when the safety lever is pushed towards the rear.