Help, stability issues

HW: CSS610-8G-2S+IN
FW: 2.18 (built at Mon Mar 04 2024 15:52:12 GMT+0100 (Central European Standard Time))

No custom configuration, just bought switch and installed it to my home. I have 6 1gbps devices attached to RJ45 connectors, no SFP+ modules so far.

Internet is going down like every 30sec for 1-5sec, then everything is back to normal. I tried network traffic test with iperf3 (256mbit/s traffic), data is flowing just fine. (PC-router)

When network is down, I cannot open web pages, MikroTik swOS GUI shows "Error lost connection". Then everything is back to normal our of the blue for 20-60sec.

is it a known issue? Does it has workaround?

Is it defective unit, should I return it?

What is wrong with it, why do I have data flowing, but cannot access internet connection? Dns issue? But microtik admin I open via ip address?

everything works just fine if I go back to ubiquiti router (8-60w).

on gui page stats looks fine, 0 errors, 51 hosts online.

please help, this is rather annoying. It suppose to replace aggregation switch in my tiny home setup. I need 8-60w to one of the remote rooms, also SFP+ will be used for NAS/PC.

update:
to make it even more fun, ping <router> always show fast times (<1ms), but sometimes I dont get reply from ping for 4 seconds, while it should ping host every second...

-----------------------

Current update2:

Some ports goes black randomly, like every 5 sec for 1 sec. Some others never do that. It depends on the device connected.
It does not like my laptop, and router. When it goes black it is reflected in web ui.

I dont see any logs in UI, port 22 is closed and I cannot login to the router. Router is factory rested.
---
one uncommon thing is I have big subnet 192.168.0.0/23 but that should not kill the switch?

-------------------

Last update:

some connections just keep blinking, like 5sec on, 1 sec off, visible on front face and in web ui.

It is enough to have single cable going to my router (pfsense box), to get it blinking. No traffic/no cycled devices for sure.

winbox/ssh does not work on this model (or ssh is off for this item?), no deeper logs can be fetched.

I will return it, will try to get replacement to test... Case closed for now... :(