If button and link tracking is your aim I really recommend you enable Activity Map.
It will then automatically give you advance link usage(button or html links). Save you custom evar programming as well.
Also in this case. If you had used lets say custom link tracking you could have seen one beacon for page data and one for custom link tracking. Is evar being setup via a sort of s.tl call?
In your analytics login here do a search for eVar29 as perhaps button name report is different than actual evar29 you defined.