Response from EventReceiver in SP 2019

Hello everyone,
I'm having a problem with an EventReceiver in SharePoint OnPremise 2019.
This Event Receiver, developed in Visual Studio, launches when a file is added to a document library.
There are 3 events:
ItemAdding
ItemAdded
ItemUpdated
In the ItemAdding event, we check that the file uploaded is a ZIP file, that the person has the right to uninstall a file, and so on.
And we return a custom error message via ctx.OutgoingResponse.

We add a file to this library from a Front application in React, using the SharePoint APIs:

The events are executed correctly when a file is added.
On my development and internal acceptance environments, it works correctly, and error messages are retrieved from the front by the code:

But on the customer's test and production environments, the message is not retrieved, I always get an empty message.

ctx.OutgoingResponse.StatusDescription = ex.Message; 

What could be causing this difference in response?
I've compared the web.config files and can't find anything.
Parametrisation at the IIS server level?

Thanks for your help