Editing XLSX files - internal server error in API

Hi guys, we've integrated your API and it has worked fine for a while now, but suddenly today people started complaining about being unable to edit Excel files.

After checking, it looks like your API returns the following response:

RESULT=FALSE

ERROR_CODE=2502

WARNING=Internal Server Error while processing this request

Problem is, this gives me zero useful information, because your API docs don't list such an error code: https://www.zoho.eu/docs/help/office-apis.html#working-with-office-apis/open

Also, Word and PowerPoint files work just fine, it's only Excel files that are affected, so it looks like the problem is on your end.

What can be done with this and when could we see this fixed?