Great use of the plugin, first of all! Thanks for providing the link, it confirms that the 1st custom url is coming out as null (empty) - leaving nowhere for the link to point to, which most browsers interpret as reloading the current page.
I still haven't been able to replicate the bug myself, but a couple others have reported this same issue. I have a hunch that it may have something to do with the first version of the plugin you used - do you know what that would be? Alternatively, if you know approximately when you first installed the plugin, I can find the corresponding version number.
You might also be able to resolve it by deactivating the reactivating it - does that fix it? I'm perplexed, because the bug seems to only effect the first custom link, but that link uses the same code as the others...
Hopefully once I can reproduce the bug, I can find a solution.