Dropping a GPU

[dTest]

I know this is a OpenCL/hardware issue and not a hashcat, but thought you good folks might have some insight.
Quick specs:
Ubuntu 14.x LTS
NVIDIA driver v.375.39
Intel i7-6850, 32 GB RAM
3x EVGA 1070's
Gigabyte x99 gaming something mobo
1500W Corsair PSU. 
*no* risers!

Temperatures stay cool/OK.
After a some time it will drop one of my GPUs

clinfo does show that its gone.  But 

Code:

lspci -vnn | grep VGA -A 12 | grep VGA

Show all three.
A reboot (even a soft reboot, aka: reboot from a prompt) gets it back, for a while.
How long it lasts is as random as can be.

Usually when it hangs its, at the beginning during initializing memory (?, initializing something)
I can do a kill -9 and it doesn't exactly stop hashcat, but gets it running with one dropped GPU
All further runs (without a reboot) will run fine with just the 2 GPUs.

Any ideas?
Is there a way to 'jump-start' OpenCL to get it back without a reboot? (as a work around)
TIA

[epixoip]

Could be an ASIC hang. You can try to use nvidia-smi to reset the GPU.

[dTest]

Thanks man!
But unfortunately, it needs a visible GPU id to reset. (unless I'm missing something)