A region file is cut short
What it looks like in your log
Region file ./world/region/r.0.0.mca has truncated header: 0
What causes it
A region file was truncated, usually by a crash or full disk during a write, or a botched transfer. Every chunk in it is unreadable.
How to fix it
Restore the file from a backup, delete it and accept regeneration, or repair the world with a region tool such as MCASelector.
Not sure this is your problem? Paste your log and Roastd will tell you which of these it actually matched, and what else it found.
Check your own log