Old "Ruby-style" .25 acp problems.

[OttoParabellum]

Im having a problems with my uncles old spanish .25 acp pocketrocket.

Problem is this:

-When full mag and gets first into chamber the first goes boom. And gets ejected.
-Second round gets into chamber automatically but when pulling trigger only lazy "knock" and fails to fire. Then rack slide manually back to **** it but still keeping same round into chamber then fires second round and gets ejected.
- 3rd round and 4rd does the same tricks to get fired than second round.

But when having one in chamber and two in mag old bastard works fine and no fails to feed or fails to fire.

Can someone give me lenght of the original recoilspring?
Mine was 50mm long and having 22 rounds.

I think mayde the recoilspring is too short because the slide goes läfew millimetres back/forward and that may cause that fail to fire problem because when the hammer hits the firing pin and firing pin hits primer and slide maybe moves forward and that makes firingpin hit is too weak to get primer boom?

Thanks for help and sorry for bad english.