SIP INVITE 408 Request Timeout with JMeter 5.6.2

I’ve spent hours trying to figure out why SIP INVITE requests are returning 408 Request Timeout errors when JMeter 5.6.2 threads exceed 50 from Singapore.

Running a simple SIP load test against Genesys Cloud. The test works fine at 20 threads but fails consistently at 50. Using the standard SIP plugin. Any ideas on the default SIP connection limits?