Elastic App Search nodes crash or return 500 when load testing

We have created an elastic cloud through Azure and have 2 engines in a meta engine. We are trying to load balance in this environment. When the elastic app search is scaled pretty low, the instances just crash, so we decided to upscale (for testing) to 3 zones x 40GB 10.3 vCPU (the maximum). This doesn't crash but returns 500 messages. Can someone help?