Latency - RouterBOARD 750g

Hello, I have some latency problems.
When I boot the router, try to ping 8.8.8.8 from a host, connected with a utp cable to the switch port of the mikrotik.
The delay is 40ms.
After a few minutes, it becomes 80ms !!!

When I replace the mikrotik with linksys, with the same position on the network and the same configuration - the latency to 8.8.8.8 is 50ms all the time.

On the routerboard i run nat, port forwarding, one static route, one bridge - the wlan and the lan, and that is all.
I cannot explain it to myself, from where is such a latency .

Could you give me some advises? Thanks in advance.

Regards

I have identical setup, and during 30 minutes I have unchanged 19ms latency to 8.8.8.8

Please make sure you run RouterOS v5.19 and then post output of “/export compact”