MP BGP flapping

There is an MPLS VPN network of about 30 routers (Cisco and Mikrotik) in the attachment simplified network diagram. 2-a Route Reflector on Cisco 3845. OSPF, BGP, and MP BGP are deployed.
When implementing the Mikrotik CCR1016 router (10.40.254.213), it turned out that if the connection between (10.40.254.217) and (10.40.254.213) is lost, the MP BGP session starts flapping between RR and (10.40.254.213) with a timeout of 180 seconds..
OSPF, LDP, BGP VPNv4 tables are all normal, pings are stable.
It helps to disable the LDP interface and enable it after the MP BGP session is established.
Tried changing OS, changing MSS. Not help.
Very similar to http://forum.mikrotik.com/t/mpls-labels-dropping-after-outage/140076/1
While using the script to disable / enable the LDP interface. Can anyone help?
Network.jpg

Changing the MTU in the network section (OSPF in the diagram) helped. There were MPLS MTU 1500, L3 MTU 1484. Became MPLS MTU 1530, L3 MTU 1500. Although the previous values work fine on other parts of the network.