20001 CheckSizeOfConnection The maximum amount of data that can be sent on a long-running connection has been exceeded.
The overall size of the file here is more then 10 GB.
Request you to take MWG GUI access-> Navigate to option Configuration->Appliance->Proxies-> Advanced Settings->Maximum amount of data per connection or request is 10240 megabytes which is 10 GB by default.
You can change this value accordingly.
Configuration-> Proxies -> Advanced Settings->Maximum amount of data per connection or request -> this value is set to 10240 mega bytes ( by default) which is 10.24 GB.
When a connection or request has transferred more then this volume the error handler will be called.
You can try increasing this value (Maximum amount of data per connection or request) and check.