In version 6.27 the L2MTU change from "RB433 series ether1:1526; ether2-ether3:1522", for RB433 series ether1:1522; ether2-ether3:1518.
Do this is normal? and the MPLS configuration will be change?

Version v6.28 has it fixed. RB433 L2MTU is ether1:1526; ether2-ether3:1522