Sporadic 502 Errors with Lambda and API Gateway

Hi, I have my Express "server" (serverless routes) configured in AWS Lambda behind API Gateway, with the Lambda having 20 units of provisioned concurrency to prevent cold starts. My API serves our Android and iOS mobile apps and our web backend. Often, on seemingly random requests, I get a 502 failed to fetch response. I don't believe I have the timeout set to anything crazy low that would be causing this, and it shouldn't be the status code it returns as the same request works upon refresh of the web app, as an example (retrying the request). It almost seems like this happens when there is less server volume rather than more. Thanks.