Big chain ring. 50-12 configuration. I've a 50/34 compact on a new 12-30 cassette, got new chain and new derailleur (medium cage) since my previous one could only do 12-27.
At first I thought it was spacers problem, so I took off the cassette and I looked at that sprocket specifically and I can see that the one tooth in the picture comes more outward than all the others. I just don't have enough info to know if that's to help shifting (a feature) or a defect
I tried to straighten it up by pressing that tooth against the concrete, it didn't do a thing so I could not possibly see how could I could have bent it, in case it's bent, so I'm assuming it either a feature or a manufacturing defect.