I am trying to identify why the device identity certificate would disappear from 10-50 or so iPads, that previously had working communication to our server.

Without doing any further tests, I thought I would check here if any one else may have encountered this problem and identify the main cause? I was wondering if this was due to doing a reset all settings option on all the iPads?

We've been running casper since around 9.2 some of the devices have been enrolled much later than 9.2 - with now running 9.7.3

See attached mdm profile for example: