I'd check to make sure the striker is intact and not broken. Don't hear of that much on the 45's but occasionally on the 9's and 380's. I'd probably order a Striker Spring and a recoil spring long as I was ordering, although the recoil spring isn't the issue.
This would require a detail strip of the slide to access the striker. You may find a bunch of gunk in the striker channel which would certainly cause these exact symptoms you mention.
There's a detailed post on how to do this. I'll have to look for it. One thing of note. When you do this, you need to depress the extractor channel to remove the back plate. The hole for this upper right hand corner of the back plate is deceiving. The actual access to the extractor channel is smaller than the hole appears. If you don't feel spring pressure as you push, your too big. I use a small jewelers screwdriver. Probably the smallest in the set.
Good luck, come on back if you need help.
In Memory of Paul "Dietrich" Stines.
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Cue sound of Head slap.
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