Hard freezes with Sierra

[stooovie]

I'm experiencing a really annoying freezes/hangs I've never seen before in OSX. Audio continues to play, but everything else freezes and never unfreezes. I can't even open the Force quit dialogue. Only way out is to hold the power button and then restart. Went back to El Capitan, all is fine.

I tried again with 10.12.1, and it's doing it again. Like three times within 6 hours. Rolled back again.

The usual dance of PRAM/SMC/permissions/reinstalling combo update didn't fix it.

This is a 2015 5k iMac. AHT and memtest pass OK. Anyone else?

 

[Iniura]

Yes I have the same problem on 12 inch macbook, I usually wait like a couple minutes tho and then it responds again.

 

[Greene]

This happened to me today. I don't think this has happened to me on mac since the weird powermac G5 bug. Not even on windows for the past few years.

Downgrading to Capitan on my work machine is happening soon, because that could really suck.