The change in syntax from:
protocols {
bgp <ASN> {
...to:
protocols {
bgp {
local-as <ASN>did not happen automatically on my configuration and the failure was entirely silent.
As a result, after reboot, my router (which is remote and depended on BGP to be reachable)
ended up loading none of the BGP configuration stanzas and I have had to manually reconstruct
them from the pre-migration file.