I have a hit that sends to adobe workspace an event (event 5) and populated an evar (evar73 = "checkout_Carla").
I'm pretty sure that there is only one call that trigger the event and the evar but, when I compare the event and the evar instances in the workspace I see a different name 1.389 (Event5) Vs 3.676 (evar instances)
How is it possible? The only solution is that the evar is sent in another called?
For a detailed explanation of "instances of..." please review this doc, here.
Most likely there are some additional image requests going out on the same page that the evar is being set. In particular, be careful to check for any click tracking your site may have. You may be able to track this down in Workspace if you filter by page name where these don't align and checking other variables that are used for link reporting.