Try setting your failover depth to 8 and retest. I don’t have much faith in some of the international carriers, even those Anveo calls Prime.
1015 is Airtel, 1001 is Lanck, 24 is Alcazar; I’m not snowed by any of them (for Canada).
25 is Bandwidth (good) and 27 is Iristel (they’re a Canadian carrier and that’s their business.)
If you still have trouble, post another SIP trace from the Anveo end.