Edited league names become blank

[omnivore]

For the past few years, a file I created has league names that disappear after a few seasons. Is there anything that would cause this behavior in the settings? I suspect I just need to rebuild the file from scratch, but wondered if anyone else had ever seen an edited file where the league names vanish and become blank. (I have the editor, so I can fix it, but not sure why it happens.)

[nine_iron]

I find blanks come when you duplicate something, you often have to redo the names even if they look Ok.

I do it out of habit now anytime I duplicate something. 
 

It still caused me a few headaches this year but I got around them.