I don't know if it's the fault of HFS+ per se, or if whether all this journalling and permissions and other extra crap added on top of the lean mean base system has brought it on, or perhaps it's the GPT partition scheme and multi terabyte hard disks, but it's frankly quite temperamental these days.

I never remember getting any file system issues at all in all my years on classic Mac OS, but in modern times we seem to have issues galore.

Randomly can't boot? Run a Fix inside Disk Utility. Files disappearing? Run a Fix inside Disk Utility. Volume mounts as read-only? Run a Fix inside Disk Utility.

Disk Utility won't fix it? Hope you bought Disk Warrior...