So there are a few tweaks you can do, (1) open the trasfer port in the breech block. Normally it has an Adjuster allen screw in the top, often you can back it off to open up the TP, and / or you can open the TP itself to about 2.5 mm to see if it improves. Do it gradually.
(2) Take the pistol grip off, on the bottom of the alloy casting is a nut attached to the hammer spring rat tail, turning it in increases the hammer pressure thus increasing the valve open time. ( but also increases cocking effort).
(3) On some a peculiar annoying fault can be the rat tail that the hammer spring slides over is often too tight, thus causing drag on the hammer actually slowing down the hammer strike. The spring should slide very easily along its length, if it drags sand the rat tail down til does work freely.