Hello a have strange problem

in router installed two NICs
1. Intel Server Adapter PRO/1000 PT (82572EI)
2. Intel Dual Port Server Adapter PRO/1000 PT (82571EB)

(82572EI) -- works perffect
(82571EB) -- in low loads (pinging another host) works fine when i try to load NIC pings sudenly stops with timeouts and time to time on rear panel NIC LEDs Stops lights and after second lights up again . after load removed, remote host strarts to ping again

My CPU i5 4Cores MB Intel with P55 chipset
RouterOS 5beta6 and RouterOS 4.11

please help me

Hi,
did you tried this?

solved it's my mainboard issue
replaced to new one and everything ok now