You might want to re-run memtest on some machines before discarding systems as broken. Some Minnowboards were failing memory tests. Intel looked into it and says:
We have tracked down the issue and found that memtest86 tool is using a function call with rare but legitimate NULL value which causes memory test failure.
Currently we are working to update BIOS firmware with fix to prevent this memory test function call failure from memtest86 tool.
Again this is protocol interface issue between memtest86 and our FW driver, there is no hardware issue found with memory on Minnowboard.
See elinux-minnowboard thread for details: