Server crash: models/error.mdl couldn't be loaded

Daily, sometimes twice a day, my Garry’s Mod server will crash with

After the server goes back up, that exact model will load fine.

The NFO support people are pretty much stumped, any suggestions?

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No lua errors, nothing. That’s the only error within the last 5 lines of the server log

If you have access, run an update on the server and it should update broken/missing files.
If not, ask NFO to update it for you.