I am running High Sierra 10.13.5 beta 2 on an SSD that is pretty full. It's 2TB and has about 18% free space. Since I am going on vacation I decided to go to FileVault2, which I have used previously in earlier versions without trouble and routinely use on my MacBooks. Forecast completion went from 6 hours to days. About 4 hours into the process the system "went away." Finder lost its windows, apps disappeared, and I got the ball. I rebooted, but this pattern returned in minutes I did a disk check from another partition and there was no problem. But even booting and mounting into another High Sierra ended up crashing the system. I ended up wiping the disk completely from Lion (which also crashed in the process) and then checking it in Windows 10 with Admin tools. I fired up my CC clone and booted into it (it was only a couple of days old,) formatted and restored the drive in HFS+. Then refreshed a couple of areas that had changed with TimeMachine. A day of trundling. Also updated to beta 3. Will not try FileVault again unless I have extra time on my hands. Has anybody had similar issues?