Thank you all for the suggestions, I will investigate each one.
On the possible cracked grip, that was the first thing I considered. A new grip was installed but the problem remained.
I have two new 9lb recoil springs that I'm going to try this weekend. One is a variable and the other conventional. I suppose it's possible this could be the cause but since the gun will run 100% with this load in new brass and a 10lb spring, I'm doubtful of any improvement.
On any changes to the gun from when it ran to now, there were no changes made.
The weekend before this problem occured, I had shot a 150 round club match with twice fired brass and it ran flawlessly as it normally did. The gun was cleaned after this match and dry fired the following week. I went for my weekly practice session the next weekend, using the same ammo that had run fine in the match and had 7 failures to eject. Needless to say, I was stunned. The gun had never done that before.
After trying to get it to run with once and twice fired brass without success, I loaded new brass and it functioned fine. Next I decided to try new and fired brass in the same session.
I took 400 rounds, 200 new, 100 once fired and 100 4 times fired. The results in order of firing were,
100 new brass = no failure to eject, all spent cases landed 6 to7 feet away.
100 once fired brass = 2 failure to eject, spent cases landed 4 to5 feet away.
100 4 times fired brass = 6 failure to eject, all brass landed 1 to 2 feet away
100 new brass = no failure to eject, all brass landed 5 to 6 feet away.
All rounds were fired without any cleaning or lube being done during the session.
I find it puzzling that the gun will have a total of 8 failures with fired brass then run like a swiss watch with new brass. The failures do not seem to be mag dependent either. They occur regardless of which mag is in use. In fact, I can chamber a round loaded with fired brass, remove the mag, fire the chambered round and get the same failure.
I will confirm my load PF on a different chrono this weekend in case my chrono is lying to me.
The powder charge weighs out to within .1 grains of what it has always been so, I don't hold much hope of excess pressure being the cause.
Thank all of you for your help. This is truly bizarre. I'm open to any and all suggestions.