1Dx and 40mm 2.8 STM
I should probably do a better search before asking this, but I noticed a strange occurence after mounting the new 40mm 2.8 STM on a new 1Dx body. After awhile, the camera would start to act strangely. Changing the mode and spinning the dial would result in a laggy mode "switch." Eventually, the lens would stop focusing.
Pulling the battery and all is fine. No problems with any other lenses.