You guys are starting to lose me.

Take the Bolt out of your Krag and observe the action of the Trigger/Sear, as you slowly pull the trigger.
The first-stage should cause some lowering of the sear. The second-stage will complete the lowering of the sear.

When you slowly ease up on the trigger, the process should positively reverse itself. (You can hear and feel the mechanical contact of metal surfaces, both ways).

If the 'return' of the trigger & sear is vague, the Trigger-Spring might be weak (or a poor replacement). The other possibility is poor Stock fit and interference.

If everything is moving correctly, put the Bolt back in the rifle and move the Safety to the 'Safe' position.
Repeat the trigger sequence. The trigger should feel, sound and operate the same as when the Bolt was removed.

Fred's Main-Spring is obviously strong enough to fire the rifle! (I don't recall any mention of misfires)?

If trigger action has been vague with the rifle fully assembled, remove the Stock and repeat the above sequence.
If things work correctly with the Stock removed, the problem must be something about the fit of the Stock to the metal.