Late response, but I have been getting great consistency doing a few things with the Sortie. Remove the barrel shroud clean and lightly grease where the piston slides. Verify the white plastic collar is secured with set screw to barrel. Check cycling at mid pressure, topped off cylinder is often too much pressure for the hammer to overcome, too little air released and no cycling. Don't use an LDC, the back pressure increases quickly killing the semi-action. Loosen the barrel tip, check and adjust again finding minimum tension needed to close bolt. Remove the long hammer adjustment screw and replace with short screw and longer spring. The long spring has a larger sweet spot with less tension required for cocking, makes for easier cycling. Try different pellets, domes seem to cycle better than waddcutters, I think it may be a reduction in closing effort needed.
My .177 Sortie cycles 28 shots without fail, only too high or too low cylinder pressure stops it. A very fun gun that shoots from rest 3/8" groups at 25 yards with JSB 8.44 , off hand not so much (working on it).