OK, but all my routers are using RouterOS 6.42.10 (long-term) and I want to keep it that way. I need stable IP cloud service too.As @normis hinted: problem is there for devices with ROS <= 6.42 ... devices with ROS >= 6.43 are OK.Maybe the problem is with the long-term version only?
Thank you for this, but as I say RSTP is off on all devices and I upgrade all devices to the lastest version.Switch rstp off. Or upgrade all routers to the same Ros version.