Strange problem connecting to furthest router

Hi,
I'm new to this site, but have a very strange problem with my Belkin F6D4050ea receiver. It occasionally connects to the router that is furthest from it, with a weaker signal. It doesn't do it all the time, but it's frustrating when it does, as it becomes stuck to it and I have to disable the receiver and flush the DNS to try to get it to lock on to the stronger signal.
I've never come across this problem before and I was wondering if anyone on here had, and maybe knew a fix.
Many Thanks
TheStewie