I found that adding 4 memory sticks into this board decreases the memory voltage below 1.5v (1.42V in my case).
This works, but not always. After about 6 months with spurios errors, I decided to remove 2 sticks (now for a total of 8GB). The memory voltage increased to 1.52V and things look a lot better now.
I tried various brands, currently I'm using Kingston valueram types (4gb, 1333)
Thanks for your advise!