DevonThink is a great app, but it’s not set-and-forget. You need to do a little maintenance to keep your data safe.
And backup is more important than ever; unlike Evernote or Google Keep, you’re not syncing your data to someone else’s server. Continuously updated backup services, like the very popular and otherwise excellent BackBlaze, can create problems. Arq seems to be OK. More on the DevonThink blog.