What SFP module you use?

GigaLight 1.25G SM 1310/1550 (so like S-35/53LC20D)

Is the SFP module a compatible one ? Network diagram ? It should be, according to the wiki: MikroTik devices and SFP/SFP+/QSFP+ modules do not have any restrictions for other vendor equipment. As long as the other vendor modules and devices comply with transceiver multi-source agreement (MSA) they ...

This problem happens only when SFP module is inserted - probably because then ethernet ports share all the same lane and the SFP gets its own private lane to the CPU. After some time (could be days or weeks, sometimes only hours) other interfaces stop working - RB sees ARP table, but I don't have pi...

S-3553LC20D should be compatible (based on https://wiki.mikrotik.com/wiki/MikroTik_SFP_module_compatibility_table) but i get constant link up/down on latest OS+FW (6.44beta20) 12:56:00 interface,info sfp-sfpplus1 link down 12:56:02 interface,info sfp-sfpplus1 link up (speed 1G, full duplex) 12:56:03...

I tested S-3553LC20D and it indeed occurs even with this SFP.
It's sad that Mikrotik isn't doing anything about this problem, hell can't even admit this error and claims:

We are trying to replicate this issue with our own modules, but we are unable to observe such linking issues in our labs.

thanks, I missed that...will continue there

I missed this post so I created new one...I'll copy it here to have everything together: After cold reboot (power off, power on) occasionally SFP doesn't get link up. SFP diagnostic works normal, even values shown are the same as when it has link. I tested SingleMode (1550/1310 nm) SFP brands: Optok...

After cold reboot (power off, power on) occasionally SFP doesn't get link up. SFP diagnostic works normal, even values shown are the same as when it has link. I tested SingleMode (1550/1310 nm) SFP brands: Optokon, GigaLight and 2 other Cisco compatible, I read on czech forum Maxlink SFP has the sam...

snmp for traffic seems ok, problem is with ethernet stats - see attached comparism between console and SNMP
I use latest MIB (201604010000Z)

while it seems log messages has been fixed, there is still some problem with SNMP counters which shows lot of packets for Tx Multicast, Tx Collision, Rx FCS Errors - it doesn't correspond with interface counters at all, maybe they'll mixed in SNMP and show other values instead...

Bug is still here, at least on RB450G and RB750G I first reported this bug on 23 Oct 2012 (version 5.21), then on 23. Nov 2012 (version 5.22) and again on 30. Jan 2013 (version 5.23) I'm no longer surprised that bug is present in v5.24 - according to the last official reply "it's fixed in v6 RC...