GPU problem need advice/help!

[neogeo]

From past three days have a problem with my mining VGA GPU. It is MSI RX 470 Gaming X 8GB.
Whatever i set in After Burner, after a 10 minutes of mining GPU frequency reduces from 1100MHz (locked in AB) to 600MHz-900MHz and my Hashrate getting down from 27Mh/s to 21-22Mh/s (digging ETH).
Tried to swap PCIE slots on mobo, USB riser, GPU frequency from AB, memory frequency (also from AB), GPU Voltage from AB, to increase fan speed, checked 8pin psu cable... but nothing to help
GPU clock lower down after a couple minutes of a mining and scaling from 600-900MHz.

Any idea or advice for help how to resolve problem??? (this happenes only on that one card, all another working good)

TNX

(rig: Corsair rm1000x, ga-970a-ds3p, usb risers, 5x msi rx 470 gaming x 8gb...)

[lionking477]

Have you Tried to Turn GPU Scaling on AMD Graphic cards have GPU scaling feature.

https://www.weebswire.com/what-is-gpu-scaling/

[xxcsu]

Check your gpu , gpu mem real temperature , its can be a thermal throttling issue.
Try to keep gpu, mem temp under 76 C for rx 470 card during mining, some card working fine over that temp , some card are thermal throttling.
If its a older card and it was running hot for longer time period , the thermal compound between the gpu / gpu mem and the cooler maybe leaked into your riser , mobo or to the gpu card istelf. If this is the case, replace the thermal compound.
So Check the temperature for your slower hashing card and another cards, my guess is the card you have a issue with , probably have a higher temp than your another 4 cards in that setup. Also make sure the cooling fans are working properly .