Intermittend InvalidSignature error when retrieving object from S3 Object Lambda accesspoint in lambda@edge function

We have created a lambda@edge function (nodejs 14 with default aws sdk) that retrieves an object from an S3 Object Lambda accesspoint. Most of the time everything works correctly, but from one moment to the other the lambda@edge function fails the call to S3 with an "InvalidSignature" error.

We create the S3 client once during the lambda@edge during the startup of the lambda@edge function and only do an s3.getObject call to the S3 Object Lambda accesspoint and return the results.

Any idea what could be the cause?