I am not expert but my A2s did not have this problem due to much bigger tower chassis and temps are manageable. This new shoebox like chassis design definitely has not been thought through and has become a heat magnet... and it is serious enough to offline boards.
I have discussed with my ISP on my batch of 6 x A4s arriving at their DC next week, and perhaps paying attention to where the A4s are located in the DC to get lowest ambient temps, and getting box fans for good measure to further aid cooling of chip temps.
If all that fails.... let me know where is the tallest bridge, so that I can contemplate jumping off it ...
I am running box fans with my A4's and does not seem to help. My temps according to the miner have never gotten high since the ambient temps where the miners is quite cool this time of year where I run the miners. So I don't think it is temp related.