i have been back to this thread several times as i also have this issue
the store where i bought the case have been extremely helpful
unfortunately without solving the problem
i have likewise received a cable from Thermaltake directly, with the same issues
best i've managed going through a total of 5 replacements (6 total including original)
is that my EVGA GTX980Ti Classified connected through the Riser to a Asus X99 Sabertooth
would run at PCI-E X8
but with WHEA related windows crashes as a result
i have here on Black Friday purchased for another build, a Deepcool Genome Case which also features a vertical GPU mount option, tho the Riser Cable is supposed to be sold seperately!
turns out it was included, so i decided to try this particular Riser with some ziptie magic and a makeshift non conducting stand
and what would you know
works perfectly, its neither powered or in any visible way different, apart from
the PCI-E Slot is angled 90degrees and the slot itself is reinforced with metal
Sad to say, i believe the quality of the riser on the P5 for highend GPUs / Mainboards, is simply not good enough
Surely changing suppliers for the PCI-E Riser is possible ?
Deepcool retails this PCI-E Riser for 19.95$ (tho after tax EU price is around 25â‚¬ via amazon.uk)
but for the danish market, it is on backorder at all retailers
while writing this i have been running a render test in GPU-Z to verify my PCI-E Speeds
happy i can finally use my GPU block and get it watercooled and finish this build!
not happy i had to go to a different manufacturer to get a working riser!
Asus X99 Sabertooth Intel 5820K (overclocked to 4.5Ghz) (cable tested at stock and at overclocked settings) G Skill C16 3200mhz 32GB quad channel kit Corsair RM1000 EVGA GTX980Ti Classified (also tested with a Quadro K620, GTX670, GTX690, R9 290+290X) Custom Watercooling only on CPU atm