Windows 8 cannot find more than 2 of 3 DVB-T2 290e tuners

[tutartis]

I recently had a windows 7 setup happily using 3 PCTV Systems DVB-T2 290e nanoStick tuners.

I have updated the system to windows 8 and find that although individually I have proven each tuner works, if I just install 2 tuners and run 'Set UpTV Signal' it finds them OK
however it I add a 3rd tuner and run 'Set UpTV Signal', it only finds 2 tuners:(

Any ideas I could try?

Thanks
Wayne