Fail to Extract is USUALLY a problem with the tension on the extractor.
Fail to load last round...usually a spring issue with the magazine.
I have an UC II - .45 ACP. I had several issue you describe.
1 - Replaced inner and outer springs with Wolf (8.00 or so)
2 - Ditched the Mags...they tended to gouge the alum frame. The springs in the Kimber Mags = not good. Replaced with Wilson Combat
3 - Adjusted the tension on the extractor...sounds like either too much or too little... I'm banking on too little.
Once I tuned the UC... it has been flawless. I change the springs every 1000 rounds or every year...whichever comes first ...as it is a carry weapon, and do not want a malfunction of any sort.
I do not push a lot of rounds through this one...it is for protection, not plinking. I keep it tuned and in top condition. with a little maintenance, the Uc's are an awesome weapon.