Hey Ziggy89,
First, London is a pretty big area to cover, you may want to give something like an intersection to see if anyone else in that area has issues.
Secondly, this sounds like a signal issue, as to what's causing it, several factors could be at play. I would suggest you post in the »
/fo ··· avdirect forum for us to try to see if we can find what's causing the issue & open a ticket if required.
Hope this help.
Martin