Visitor visits no longer grouped together

I tend to use Visitor Paths more than anything else.
Previously the visits from a visitor on the same IP were grouped together.
I'm now finding that some visits are grouped but a lot of the time there not.

This is making it extremely difficult to track visitors as one visitor (IP) can now look like multiple visitors.

I currently have someone on a site that would have previously been grouped so it was easy to see they were on there, they are now appearing as 20+ different visitors (all with same IP number spread over an hour.

Has a setting changed, is this a bug, how do I get StatCounter to group all visits together again?