I'm running two of the mentioned switches in combination with a S-RJ01 SFP module on both ends. The switches are connected via a CAT6A cable of 1m and the SFP modules.
Running a ping from RouterOS (default factory config) from one switch to the other and vice versa, shows a packet loss of 2-10% on one of the switches only. The direction where the packets get lost switches from time to time. One time it's from switch A to B, another time it's from switch B to A. I also have replaced the cable (CAT 5e, CAT6, 0,5m, 2m, etc.) and tried both SFP ports on both switches. On top of that I've tested RouterOS 6.47. (stable), 6.46.8 (lts), SwOS 2.11 and 2.12 (pings test with one end device at every switch) with the same results. There is nothing else connected to the switches.
The only way I have figured out, to get rid of the packet loss is to use the S-RJ01 on one side only and use regular port on the other end. And again, it doesn't make any difference on which switch I use the S-RJ01. Therefore I don't think it's an hardware related (switch or S-RJ01) issue.
Does anybody have an idea what is causing this problem?