Same situations here with Gigabyte 8 GB Gamings version, new or old. At +56 degrees they crash and memory errors, and noticed when lower is more rarely. memory oc 2150, or 2050 for new 1500 timing version.
For me the hangs and miner restarts was because undervolting too much gigabyte gamings. 850 for memory not liked, back to 900 seems better. less or no opencl hanged. not problems from driver or claymore, i think.
For those who experience OPENCL hang - guys, i recommend you to try lowering you cards temps. However this is kinda tricky with some cards. I will explain below
For my Gigabyte rx580 g1 4gb i experienced same problems - no overclocking at startup sometimes (also - try to delete afterburner profiles for this cards and apply overclocking via Claymore) and after 4-8 hrs mining - opencl error, claymore restart or system hang - especially day time when it gets warmer - so all hangups i got at day time.
The thing is - the card was undervolted and overclocked - no HWinfo errors or something, doing 29.5 mhs ETH and 64 LBC in dual mode, but still this error with opencl.
Then i checked the average temp during mining - it was about 73-75 degrees which is pretty high as i assumed. I have installed the 120-120 fan for additional cooling - but the RX580 series uses some smartass cooler management - so basically the card just lowered down it's fans RPM, keeping the same temp - about 73 degrees.
After some research - i have decided to go risky way and modify BIOS as no other means of controlling fan-temps worked for me - even claymore temperature control was causing system hangs.
I have used SRBPOLARIS editor to make changes to GPU "Target temperature" settings - i have put 68 degrees here and flashed card. (No other fan settings affected the fan behavior)
After that, the card works perfectly fine for more than 72 hrs .
I think the card was heating up way too much due to Gigabyte ineffective cooling and stock fan settings - especially memory chips, what caused driver reboot and overclocking reset.
For those who need help with this mod - contact me, also i can help with memshift mod.