BYOC SIP Trunk 503s at 50 CCR?

Hey everyone, I’ve run into a really strange issue with the BYOC edge configuration. JMeter 5.6.2 from Singapore hits 503 Service Unavailable on SIP INVITEs once concurrent call rate passes 50 per second.

Using platform API to provision trunks. No firewall blocks. Is there a hard limit on the edge capacity for new sessions?