Can not add new snippets

After update to 2.2.1, i get this error on saving an edited snippet or on saving a new snippet:

Failed to save snippet – has it changed?

Reverted back to 2.1.3.1 and got this on activation:

The plugin generated 492 characters of unexpected output during activation. If you notice “headers already sent” messages, problems with syndication feeds or other issues, try deactivating or removing this plugin.

• This topic was modified 7 years, 8 months ago by Jacob N. Breetvelt.