I'm not sure if this has been mentioned before, but I've noticed that setting an aggregate for an IPv6 prefix in BGP shows as origin code incomplete on ebgp neighbours. This is a problem because origin is chosen before MED, so the actual shortest path to the prefix is not being determined correctly. Incomplete should only be the result of redistribution, not aggregation. In the GUI, however, the origin is showing as EGP!!!

/ipv6 route print detail where dst-address=2a07:6xx0:4010::/44
Flags: X - disabled, A - active, D - dynamic, C - connect, S - static, r - rip, o - ospf, b - bgp, U - unreachable
0 ADb dst-address=2a07:6xx0:4010::/44 gateway=fe80::e68d:8cff:fe3a:4218%vl113-Leckwith gateway-status=fe80::e68d:8cff:fe3a:4218%vl113-Leckwith reachable
distance=120 scope=40 target-scope=10 bgp-as-path="65004" bgp-med=141 bgp-origin=igp bgp-communities=no-export received-from=LEC.DR1-v6

1 Db dst-address=2a07:6xx0:4010::/44 gateway=fe80::e48d:8cff:fe1b:367c%vl114-Cockett gateway-status=fe80::e48d:8cff:fe1b:367c%vl114-Cockett reachable
distance=120 scope=40 target-scope=10 bgp-as-path="65004" bgp-origin=incomplete bgp-communities=no-export received-from=COC-DR1-v6

In the output above, the second prefix is the closest (MED=0) but the origin code means it is chosen as the worst path.

RouterOS 6.35