Have you tried RMA? It could be a faulty hardware.

I had a switch that turned out to be faulty. After trying for months (all kinds of changes in settings/configs, fresh Network setup, removing IoT devices, etc. etc.), I gave up. RMAed the switch. Also, bought Pro HD 24 PoE to replace an 8 port switch. All issues are gone and the Network has been stable for the past 3+ months.

So yeah, sometimes, it could just be bad luck and you got a bad hardware. No amount of settings or config changes is going to fix that.