Tokens rendering with span tags around them

I'm using a token in the email subject line, but when I send myself a sample email, it renders as <span><span>Subject Line</span></span>. The same token renders fine in the body of the email (without the span tags), so what is different with the subject?

I'm also seeing these span tags appearing in my calendar file when I use a token in the description box. I can just put the info in manually, but I'd like to save time with tokens if possible. Has anyone else seen this, and what's the remedy? Thanks!