Are you running any servers that use Forge? Or any mods? It might not be Forge mods, but those seem to be the ones causing problems.
When I had problems like this, it turned out MineOS was crashing because of certain mods in my Hexxit/Forge server - namely Chocolate Quests, Battle Towers, and Zelda Sword Skills (see Ubuntu 14.04 MineOs-node wont start).
The effect was that while the server had crashed, the web pages still appeared to work until I did a refresh which then gave a server unavailable error until I restarted the server. At which point the Hexxit server would crash the MineOS instance again, after a period of a few minutes.
It sounds like hexparrot may have a handle on the cause of this (see Servers automatically restarting and nonresponsive UI which describes issues with fireworm and how some Forge mods might be updating files), at least this sounds like the problem…
Hopefully this helps if you are running any servers that use the Forge mod-loader.