Just what it says on the tin: If you're working on a 60fps cart you cannot use 'resume' as that will switch you back to 30fps mode.

Tested on Windows 10 v1607 and Linux 64-bit on Ubuntu 16.04.2 LTS

Confirmed on OSX Yosemite and Ubuntu 16.04.2 LTS. It was actually fairly useful for me developing my first game as it runs at half speed and I could see what my physics was doing :) But definitely a nasty bug.
Fortunately my current project is 30FPS.