Our devops team are seeing users who can no longer authenticate using 2FA code generators because their phones are off by over 30 seconds. The offset seems fairly random - a quick poll in our office shows that it appears to only impact iOS9. Mine is off 3.7 seconds. The biggest offset I've seen is 41 seconds.

Reboots, setting manually and the n going back to auto etc don't fid it.

You can check your offset at http://time.is or by downloading the free Emerald Time ntp app.

Any suggestions for a workaround greatly appriciated.