As reported by Nick Wolf.
The disk filled up on their tablet server, resulting in a bad metadata file being written. This was the error message on tablet server startup:
F0309 06:57:50.281460 32105 tablet_server_main.cc:49] Check failed: _s.ok() Bad status:Corruption: Failed to load FS layout: Could not read records from container
Could not read body from proto container file
File size not large enough to be valid: Proto container file
tried to read /var/lib/kudu/tserver/data/b1940ca83ce44da3bc6bf4a36f3d5e90.metadata
bytes at offset 30 but file size is only 114688