[L735] Two phones won't connect automatically to known wifi networks!

[Supra Edd]

I have 2 Lumia 735 mobiles. Both of them have trouble connecting automatically to known wifi networks. Easily 9 out of 10 times they won't connect when I walk in range.
Is this common amongst others at all?

To try and fix I have removed the networks re-added them, I turned the automatic on/off etc etc. But nothing makes a difference.

Thanks,

Edd...