Hi Sandy,
This is not because of SFP+ modules. I understand that you advise to use Intel SFP+ modules but there are other vendors that make compatible SFP+ modules.
As for my problem, there were problem in Linux kernel version 3, some part that works with fragmented packets. In kernel 4.2 there is some changes about this. So now it works stable for more than a week.
Thank you for a participation.
Sincerely,
Evgeny.