I was testing my new Sigma 24mm f1.4 yesterday and realized that I could not stop it down below 4.0. So I mounted my (also new) 50 1.4: same thing. Then I got out my 100 2.8 macro and found I couldn't stop that down either. Went through all the menus...
That was it. And here's what's weird. I saw that menu as I was going through everything, and I did notice it was set to 4.0. I changed to 1.4, pressed the Set button, and exited. Didn't work. After I saw your suggestion, I returned to the Set Apertu...