High latency on EWS when loading outlook

Recently updated from exchange 2010 to exchange 2016 cu1, most things seem normal but when a user opens outlook it causes a huge spike in latency...

running:

Test-OutlookWebServices

Source                              ServiceEndpoint                     Scenario                                  Result        Latency(MS)
------                                    ---------------                     --------                                    ------         -------
server.domain.net            mail.domain.net                   Autodiscover: Outlook Provider     Success      20
server.domain.net            mail.domain.net                   Exchange Web Services              Success   25655
server.domain.net            mail.domain.net                   Availability Service                     Success    1022
server.domain.net            mail.domain.net                   Offline Address Book                   Success      20

But if I let it sit that number will go back down to expected low numbers.

I am also getting a lot of eventid 5011 events: