@mtimms2,
Sorry to hear you also have a board that fails when using the Epiphany cores. On the other hand it seems it is not quite such an isolated incident as just my one board.
Have you tried allowing the board to run warmer as I mention in a previous post:
viewtopic.php?f=50&t=1438&sid=8f1a61350979fc73303884fb460b8ff2#p9488?
I did manage to get my really dodgy board to execute tests for just over 24 hours by keeping the temperature reported for the Zynq chip above 65 degrees C but mostly below 70 degrees C (I think it spiked briefly at 73 degrees in the warm late afternoon before I could adjust the airflow!).
It still locked up eventually however. My brother,who many years ago used to work repairing micro computers, mentioned that in his experience when a board works better when warm it usually indicated a bad joint which became less bad (as it were) under heat expansion. If this is the case then who knows if such a fault occurred at manufacture, transit or installation. On the other hand it could be some other fault - maybe signalling or timing. No one else, you might have noticed, has come forward to offer any possibilities and things that might be looked into to help track down the problem
I have now removed this board from my mini-cluster and am in the process of replacing it with a new 7010 based P1601 (its the 2nd - the 1st lasted about 24 hours before being dead and was replaced by RS - I am doing burn-in tests on the replacement before installing it in the cluster so if it fails I will not have made any changes such as bridging J15 for power via mounting pads).
The bad 7020 A101040 board I will use for non-Epiphany development and experiments - learning a bit about FPGA programming would seem an appropriate use. I did not try to RMA this boards as firstly I would have to get it back to Adapteva in the USA from the UK, and secondly in trying to sort out what was wrong I blew the 4A fuse on the board while trying to check the 5V test point (which is surrounded by grounded things) and had to bridge the fuse - not as expertly as some I just made a solder bridge.
However, all my boards, including the new 7010 P1601 incumbent, exhibit the 'soft' failures with matmul-16 and fft2d. The new board is being powered during 'acceptance testing' via the barrel connector using one of the wall-wart power supplies supplied by Adapteva as part of my mini-cluster reward - maybe it will improve when I connect it to the 5V, 12A supply shared by all mini cluster boards and their network switch, but I'll not be holding my breath...