Good evening, I have a question regarding RX480 cards.

I have a 12gpu rx480 rig with modified BIOS. While "only ETH" mining 1 random GPU from time to time drops hashrate to 0, and the whole rig restarts. It happens ~1 time per hour.
When I switch to dual mode, the same thing happens within first 3 minutes and then very often rig doesn´t restart by itself like it does in eth-only mode, but turns off.
No undervolt/overclock, just default settings.

Did anybody have the same problem? Are rx480 cards just unable to dual-mine? Could it be because of modified BIOS? I´ve also tried to increase/decrease power stage (5-6-7) and core voltage(900-1100), no results. Any info is appreciated, max rig uptime i have ever had was just under 2hrs... Thanks!

https://imgur.com/a/tlILY