It appears to be an issue with nicehash control -- I have this issue with any CCminer 1.1, 1.2, and the latest NVMiner build.

Behavior only present on auto-switching.

The behavior is present across multiple rigs (780 rigs, 750ti rigs). Running the miner with a built in pause command does not change the behavior either.

Again, it still generates shares, but they are either not submitted to my deposit address, or it is running in benchmark mode.