I am currently facing an issue where the RadGrid export fails with an Sys.WebForms.PageRequestManagerParserErrorException (Client-Side) when trying to export a filtered grid. I am using the custom DocumentProcessing described in: https://www.telerik.com/support/kb/aspnet-ajax/details/export-large-amount-of-data-to-pdf-xlsx-and-csv-using-the-telerik-document-processing-libraries
However, the data that is generated is fine. Also, it works when doing custom search through another Textfield / Button. The issue only occurs after previously filtering the grid. It seems like the source for the http request is false and the browser is not expecting a document to be returned. Instead of "document" as http request source it says "xhr". (see attachments: first one shows the error, the other the working request) When opening the request in another tab it works fine as well.
Could anyone help figure this out?