Nvidia rig issue

Hi all.

I've assebled next rig:
ASrock B250 Pro4
Intel Pentium G4400
4GB RAM
Thermaltake 1000W
5 x 1070 MSI ARMOR 8G OC
5 x v006 molex-risers.

OS: Win 10x64 or Win 7x64 (I've tried use both of it).
nVidia driver 378.92
Miner: EWBF's CUDA Zcash miner 0.3.3b

So, periodically one (random) Video Card is stopping. After that only reboot of PC available for mining continuation.

Temperature about 63 to 72 degrees. Overclocking is off.

Last issue after ~7 hrs mining:

Code:

INFO 04:37:45: GPU3 Accepted share 44ms [A:639, R:1]
ERROR: Looks like GPU0 are stopped. Restart attempt.
INFO: Detected new work: 1490996991
INFO: Detected new work: 1490996992
INFO: Detected new work: 1490996993
INFO: Detected new work: 1490996994
INFO: Detected new work: 1490996995
Temp: GPU0 52C GPU1 57C GPU2 46C GPU3 0C GPU4 53C 
GPU0: 416 Sol/s GPU1: 413 Sol/s GPU2: 419 Sol/s GPU3: 416 Sol/s GPU4: 418 Sol/s 
Total speed: 2082 Sol/s
CUDA: Device: 3 Thread exited with code: 30
CUDA: Device: 1 Thread exited with code: 30
CUDA: Device: 4 Thread exited with code: 30
CUDA: Device: 2 Thread exited with code: 30
CUDA: Device: 0 Thread exited with code: 0
INFO: GPU0 are restarted.
ERROR: Looks like GPU2 are stopped. Restart attempt.
INFO: GPU2 are restarted.
ERROR: Looks like GPU3 are stopped. Restart attempt.
INFO: GPU3 are restarted.
ERROR: Looks like GPU4 are stopped. Restart attempt.
INFO: GPU4 are restarted.
CUDA: Device: 0 User selected solver: 0
CUDA: Device: 3 User selected solver: 0
CUDA: Device: 2 User selected solver: 0
CUDA: Device: 4 User selected solver: 0
CUDA: Device: 0 Thread exited with code: 46
CUDA: Device: 3 Thread exited with code: 46
CUDA: Device: 2 Thread exited with code: 46
CUDA: Device: 4 Thread exited with code: 46

In the System Event log appeared next record
"Display driver nvlddmkm stopped responding and has successfully recovered."

I've tried to disconnect one VC, but after 6 hrs got same issue.

After the issue one VC is "disabled" in MSI AfterBurner (no overclocking, just monitoring).
Only reboot helps.

Please, help me to define cause.