So I started calibrating it, but now its stuck on Voice 12 Osc 1. Do you think its okay to power it down? It says not to in the manual but I don't know what else to do...
Yes, it's okay to power it down.
Power it back up again, wait for it to complete boot up, and then press both the "Down" and "Up" buttons and hold them, and press "Global" to access the Debug Menu.
Then under item number 1, proceed to clear the calibration data by pressing the "Write" button. Then press "Global" to get out of that Menu and proceed to calibrate the synth once again, and things should get back in order after that.
Note: the calibration might take longer since it will have to start from scratch for every voice and not take into account any previously saved calibration data. Be patient. And if it still gets stuck along the way, simply power down, and redo another calibration.
Several REV2 owners, including myself, will confirm that the calibration does get stuck sometimes on a voice, and it can take a few calibrations for things to get back on track.
If, however, after several attempts at calibration with the synth still getting stuck each time, maybe it would be time to contact DSI support about it.