Correct, they are the current stable releases. I haven't had anyone reporting issues with those.
If the units are not running the firmware that has been selected for the network the devices will keep trying to download the upgrade (and then rebooting). Occasionally you get a device that fails its upgrade and gets stuck in this cycle. This is not so likely across so many devices though.
Alas the dashboard does not report the actual firmware version that devices are running, but what they are meant to be running. You can always ask support to confirm the actual software versions running on your devices.
Seems that the issue solved by itself....quite a mistery.
I just mentioned the support the idea that Phiilip mentioned earlier: an AP that is rebooting due to a bad Firmware upgrade. The answer was that just ONE AP was having that problem and they fixed the Firmare version. ...and After that none of the other AP show any reboot.
Anyway the support team agreed that those reboots were related in a way with that firmware upgrade but also that there was still an issue on Cisco Meraki's backend that were not solved yet.
No further technical explanation so far.
I'll let you know any update in case i got more details.