IOS Self Service "Cant connect to server" issue

New Contributor II

OK Brains trust, our current dilemma being handed to me is is thus:

We are a Primary (Elementary) School have JAMF Pro hosted on JAMFcloud. 
Now, we seem to get a problem, around about 50% of the time, when opening Selfservice App, we get a "cant connect to server" message. 
If we grab another device, works a treat.
If we reset the iPad in question, 9 times out of 10, it'll work fine.

The proxy is configured correctly as per advice here:,_IP_Addresses,_and_URLs_Used_by_J...

And I would assume, if it weren't it would be failing on all devices.

Our network is 200/200mbps externally. (It's usage is a bout 25-50% during sustained peak moments) we are very rarely running high on bandwidth.
Internally, we're 10Gb backbone, to 1Gb Access points in every room. There's no bottle necks. And the behaviour happens all accross the campus.

So yeah, if anyone has any ideas on how I could look at this, I'd be grateful.