ARD - same clients keep losing credentials

I have a list of a dozen of so Mac Minis (all the same model) which I administer with ARD. There is a group of 6 of these which will randomly lose authentication every few days so the blue dot next to the machine will vanish, the icon will turn black and the computer name will disappear. After a restart or removing then adding back the network server account the login info will be retained again for a few more days. The only things I can think of that set these particular machines apart from the rest is that they once had little snitch installed (since removed - also a few server still have it installed and they are not affected by this) and they once had different profile manager profiles installed, which have also been removed. I can't find anything that seems relevant in the console on these machines around the time they lose authentication. All machines are on the latest MacOS public release. Can anyone help?