YAML error, but only on one PLT

I have two PLT-200A units. For both PLTs, the "About PLT" menu shows:

• PLT-OS: 1.5.5
• r: 1.3.31

When I send the same release to both PLTs, they both accept the release.

However, one of the PLTs produces an error after I restart it. The error message is cut off by the screen, but based on some googling, I think the full error message is:

" yaml: control characters are not allowed"

How do I fix this?