Forum Solo ads ? on Unique visitor page

As emails with links move through the internet, mailboxes and datacenter they are scanned by firewalls software and different kinds of bots as they move through servers. This kind of click can be from anything. I would consider looking at your results from solos as a whole. One bad optin or click doesn't mean the whole solo is bad, when you send to your list you know anything can happen once the emails go out. Everyones list has some percent of bad subscribers.