When I use shortcodes to protect content, it substitutes text?

I've put shortcodes on my home page so I can greet strangers to my site differently than returning visitors or members. I've used this:

[level-stranger]Sign Up for a workshop to gain access to free membership content, or to join a workshop![/level-stranger]

When I visit as a Stranger, the codes seem to be working as the text is present. However, when I visit as a member, substitute text appears where this message would have been. It reads: "Register for a workshop to gain access to all of its content! " This is clearly a sentence I've written, but I have no idea where I put it or how it is getting to this page.

Help, please, and thank you,