I have a late 2015 retina iMac running Mojave. Boot up disk is an external SSD. Three user accounts, with two of these having users file on the SSD and one on the HD.
Every couple of days when waking iMac from sleep the screen goes black/empty (but the Mac is still on). Can see the cursor but nothing else, If I press a key I get the error beep sound.
Any idea what is going on? Might it be to do with user permissions?
I think I’ve to reset the SMC and PRAM as per instructions.