Webhook data missing from cloudwatch logs and API Gateway

I'm having an issue with receiving 100% of the webhook notifications sent from Authorize.net. Currently, our infrastructure is in AWS and includes API Gateway and a Lambda function.

We set up our webhooks to listen to "authCapture" events and have those notifications being sent to our API endpoint from API Gateway. When we receive the webhook notification, the lambda function is triggered and returns a response.

While doing an assessment comparing the data from Authorize.net and data received and processed in AWS, there are some discrepancies. Some requests are just completely missing seeming like we didn't receive the webhook event for it at all.

We use cloudwatch to log all received requests that come through our lambda, and this is how we noticed that some are completely missing.

Using cloudwatch metrics, i've verified that there are no throttling errors. I've also increased the memory of the lambda function from 128MB to 512MB and have AWS X-RAY for the api gateway which shows that all received requests (100%) are in the OK status and a response gets returned on average in 3 seconds.

I've also tried Lambda function URLs, but seeing pretty much the same data come through that we receive with API Gateway, so I don't think it's a time out issue.

Authorize.net claims that they have successfully sent the webhook notification and received a 200 response from our server, but i'm not sure how that's the case if it seems like we haven't received the notification at all since they're missing from our logs.

I'm wondering if anyone knows why this could be happening? Is this likely an API Gateway issue? or Lambda issue?