I recently purchased my first MikroTik switch, the CRS310-8G-2S+-IN. I am very impressed with the switch's features and performance, but I am having one strange issue.

Randomly, some of the 2.5G ports will stop working. There is no transmit or receive activity, and the port lights do not turn on. When this happens, I can only get the ports working again by resetting the switch.

I have tried everything I can think of to troubleshoot the issue, including rebooting the switch, updating the firmware, and changing the port settings. However, the problem persists.

My topology is relatively simple: I have a Ubiquiti Unifi Dream Machine SE (UDM-SE) connected to port 10 of the MikroTik switch using a DAC cable. The UDM-SE is then connected to various other devices, including a NAS, a server, and several workstations.

The switch has been working fine for a couple of weeks, but recently, ports 1 and 3 have stopped working. I have tried rebooting the switch again, but the problem persists.

I am starting to think that there may be a problem with the switch itself. Should I RMA the switch?

You mention it working fine in beginning. Any chance the workstations on said ports have changed ( longer cable, sleep mode, LAN card driver update etc )? And by reset do you mean reboot, cutting power or complete factory reset?
But if nothing has changed and it's always those same ports, i'd suspect some failure there and apply for warranty.

Thank you for sharing your experience! I encountered a similar issue with the ports on my CRS310-8G+2S+IN when connecting my PC's 2.5G Ethernet.
The problem occurred when my PC was shut down overnight. The next day, the affected port would stop functioning entirely.
After reading this thread, I tried disabling auto-negotiation on the problematic port and manually set it to 2.5G. Once I reconnected my PC, the port started working again.

Based on this, I suspect there’s a bug with the auto-negotiation feature. It seems that when the port negotiates to 2.5G and the connected device shuts down, the port fails to reinitialize properly when the device powers on again.

I've read that this switch is equiped with 2 glued heatsinks and they can also get out due too bad glue and not correct heat dissipation.
Can you open the unit and check the heatsink state ?

I've few units runnings and this will be the first thing i'll check, mines are all racked, so they don't physicaly move