Recently found that one of my users, bob, could not log in. I tried to check the user in the Synology Control Panel > User & Group but got the message “failed to load the user data”. No other users seemed affected.

I logged in with <span class="code">ssh</span> with suspicions that some file permissions had been messed up. Took a bit of time but I discovered that some ill-advised and careless use of <span class="code">chown -R</span> in <span class="code">/volume1</span> (switching ownership of some shared files) meant that bob no longer owned the files/folders in <span class="code">/volume1/@userpreference/bob</span>.

I <span class="code">chown</span>ed them back to bob and it fixed the problem.

Sorry, bob.