[Hugh]

Spencer,

Is the toggle catching on the hold open or is it catching on the rear of the cartridge in the mag? I suggest loading one cartridge in the chamber and inserting an empty magazine. Then fire the gun and see if the toggle locks open.
If the toggle doesn't lock open:
This will tell you if the problem is a main spring that is too weak or too strong. If the main spring is to strong, the toggle will not retract far enough and hang up on the top cartridge in the magazine. If it is too weak, the toggle will recoil too fast and "bounce" forward before the top cartridge in the mag has a chance to rise far enough to load and the toggle will hang up on it.

If the toggle locks open, then you probably have a weak hold open spring. You can carefully bend the hold open spring down to strengthen it. If bent too far, however it is subject to breakage.