Redirect when clicking scroll bar - Chrome Win 10

[MrComputerSaint]

So I've got a computer to get rid of the virus and malware. It had some horrid software on, I've taken that off as it seemed to also have a redirect program in there.

Task manager and msconfig looks clean of all crap.

But I took it back to the customer and bap! There was a problem that wasn't there when I tested it. When I click on the scroll bar, seemingly of any web page, it will open a new tab and redirect to another site. It seems a random site, but sometimes redirects to the software I just uninstalled.
I've brought the PC back home with me now and it's not doing it any more now, just I'm afraid to take it back to the customer as it might do it again.

Any suggestions?

[jimbouk]

Add-on in Chrome? If they've got something linked to their profile then it might even install itself again if they've got it installed on a different computer when google 'syncs' the profile.

[MrComputerSaint]

No extensions listed, but I think I found it - DNS unlocker. After I installed Avast, I then ran the uninstaller for DNS unlocker and Avast quarantined some DLL so I've taken it from the registry.
Can't see it in the start-up etc now.

[MrComputerSaint]

It was actually something that had installed itself as "Desktop Weather Service" which was hiding itself as adware. I removed this, ran adwcleaner and malware bites and it got rid of it.