0% free HDD space on CRS326-24G-2S+

Hi, welcome to the club :frowning:.
Did you have the wireless package installed ?
Bad news: You need to reset all and netinstall - no other way that I found to fix it.
Good news: backup still work (without changes can’t be saved) and you should do before reset and netinstall.

See http://forum.mikrotik.com/t/echo-system-error-critical-could-not-save-configuration-changes-not-enough-storage-space-available/181580/7

Kim