Alright, I'm onsite now and I'm finding this issue:
The site has a bunch of AP's: MR32, MR33, MR72, MR74.
The issue is that on a few of the MR32's since the update the 5 GHz radio suddenly stops working.
After rebooting the AP the 5 GHz once again sends out RF energy and beacons. But after a few days (6 to 7), it stops again.
Other AP's who aren't used that much also have the issue but on another time.
I'm testing this with the Ekahau sidekick.
Time to give Support a call.