SEP 14.2 latest release for MacOS - scan closes after a few seconds, either the full scan or the custom scan selecting the hard drive as the item to scan. Issue is on a user's MacBook Pro running Mojave, and I can reproduce the issue on my test Mojave Mac Mini.
On the user's MacBook Pro, I have used the SEP managed client built-in uninstaller to remove SEP and installed the unmanaged SEP client latest version and ran LiveUpdate successfully, when trying to run a scan I was getting an error message : "Scan Error message saying that The scan failed because of a scan engine problem. Run LiveUpdate to get the latest version", I checked again if there was any possible updates, ofcourse there wasn't any.
On my test Mac Mini, I have used the Symantec Uninstaller script software to remove the SEP managed client and to make sure to remove the software with no leftovers left behind and installed the unamanaged SEP client, running a scan is no longer scan still last about 3-4 seconds maybe less and closes just like on the user's computer with the managed client when she called us for assistance with this scan issue.
I did some researches and couldn't find anything useful besides the following chart that makes me think it could possibly be an SEP client version and MacOS version conflict (like the latest SEP version having issues with Mojave) :
Mac compatibility with the Endpoint Protection client