Hi @Van Roekel, Bob ,
We apologize for the delay in response. sometimes this error can be caused due to the service being pushed above its limit and may not be able to keep up with the request rate. You can view this similar SO thread.
Here is a possible solution that was posted:
" Issue could be due to starvation of TCP connection pool and adding the connection settings showed improvements. To resolve other exceptions while calling Search service (Task cancelled exceptions, Http Socket exceptions, IndexBatch exceptions, Null reference exceptions, Service too busy exceptions etc), additional modifications/fix were made as per the requirement:
-Increase the service replicas.
-Decrease load on Search service by reducing calls.
-Adding delays. "