We’ve a RouterOS v5.8 running on a Intel PC. CPU has 4 cores. It works fine, but suddenly some queues stop working. Rebooting is the only way it starts working OK again.
I don’t if it has to be but I’ve noticed that most of IRQs are assigned to just one of CPU’s cores.
I read a post here that said “Contacted support, they said there are issues with multi-core systems and v5. Best bet is either to downgrade to 4.17 or wait for v6.” http://forum.mikrotik.com/t/pc-x86-v4-3-to-5-18/57796/1
Your problem could be related to that, as you have a 4-core system.