There are other forum with people informing that hashrate goes down... in TUF and MSI too the problem is that we cannot see the memory temp... Igorslab hat a Nvidia Program to see it... but we are not lucky to have it.

You can see you have a memory temp problem if you leave the fans in auto and the fans goes up and up when GPU stills cool. 

In windows if you use GPUZ you should put programs that make the Memory Control Load high... 90-100% miners are perfect. if you don't want to make the thermal mod and you have this problem, there are other solution direct cool to the card or reduce memory Mhz for example-1000Mhz. With that reduce you can also limit the power limit to 180W and you will get a fix 77Mhs... and fans want be at 100%.

We also don't know if the spin fan to 100% on memory control is done in all brands. In gigabyte we know that his BIOS check the memory temps, which is great... what is not great are the quality thermal pads.

If some opened it, he will also see that backplate come with the exact place to put thermal pads of 3mm. So they have that prepared to do it to help to reduce temp but they didn't put them...
For example I have made a stress test in a room of 35C... having 100Mhs+ fans in auto ... the hash rate was completely stable and fans where in auto at 72% and GPU Temp 63C... the memory I don't know but surely not near the 104C Trolling Memory Temp