Google WMT Turning 1 Link into 4,000+ Links

[Kingof5]

We operate 2 ecommerce sites. The About Us page of our main site links to the homepage of our second site. It's been this way since the second site launched about 5 years ago. The sites sell completely different products and aren't related besides both being owned by us.

In Webmaster Tools for site 2, it's picking up ~4,100 links coming to the home page from site 1. But we only link to the home page 1 time in the entire site and that's from the About Us page.

I've used Screaming Frog, IT has looked at source, JavaScript, etc., and we're stumped. It doesn't look like WMT has a function to show you on what pages of a domain it finds the links and we're not seeing anything by checking the site itself.

Does anyone have experience with a situation like this? Anyone know an easy way to find exactly where Google sees these links coming from?

[RobertFisher]

David

Without more data it is hard to answer this. I will ask a question and it is simply to check for the info - is the link in any way a footer link? sidebar? etc.? If there were a way to look at the link we might could help, but I can understand if not. 
Best.