Unfortunately, many of us who volunteer do not actively run a vb5 site at this time. So the amount of free assistance will of course be of a lessor amount.
I do sympathize with your frustration, and at this time I do not have an answer to your question -- I cannot reproduce it. I would think @MarkB or @Zachery over at vBulletin.com might be one of the guys/gals to ask (some support is on vacation). If your question is on a non-modified vBulletin 5 product, your question should be addressed by your support package.
This is just my opinion - I am just a vb enthusiast.
If I dig anything up, I will PM you.