Tiles on start page resize and rearrange on reboot

I searched for this but nothing turned up. The tiles I've put on the start page for various apps (all resized to small) and arranged in groups are rearranging themselves randomly and resizing to medium each time I reboot. I can't find any reason for this. Also, is it possible to start more than one app at a time using the tiles? I've tried searching here and using Google but nothing at all comes up. Could be poor search keywords but any suggestions would be gratefully received. It's a clean install after upgrading.

After several reboots it's just stopped doing it. Again, no apparent reason.