Sorry to hear this. But it sounds like careless system management. I work at a lot of video shops and none of them are even on Sierra, let alone High Sierra. Up

Sorry to hear this. But it sounds like careless system management. I work at a lot of video shops and none of them are even on Sierra, let alone High Sierra. Update one laptop and test. Apple has put AFP on the backseat for several years now (since they switched the default in Mavericks), in favour of SMB2.