At some point I was considering faulty hardware due to bad VVRP packets checksum. So, I have decided to use another switch to have the LAN trunk from MX connected to. Once the MXs were connected there the problem was resolved. So, I went back to original switch to see what the difference is when i noticed on the original i had stp guard - bpdu guard active on these ports! After disabling stp guard on the original switch - all went back to normal. While in the documentation recommends enabling RSTP globally, it doesn't mention not to use STP Guard for those ports as it will cause issues.
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