Hi vasudhevan,
Thanks for your interest in the NXP MIMXRT product, I would like to provide service for you.
Do you mean, when you use the RT1064 SDK related code, your TLS1.2 can work with the HTTP right, but when you use the MQTT with TLS1.2, you meet the handshake issues.
In the previous time, about the TLS1.2 handshake issues, I meet one customer, but that customer still use the HTTP, just import it the customer's project, and add other code like SD card and others.
At last, his issue is caused by the memory issues, it is resolved by changing the define "configTOTAL_HEAP_SIZE" (file FreeRTOSConfig.h) to the large value, eg: 150 * 1024.
So, I think you also can try to set large configTOTAL_HEAP_SIZE on your side, whether that is helpful on your side or not.
Wish it helps you!
Best Regards,
Kerry