Answer
Since this doesn't match the documented capability, narrow it down systematically rather than assuming a platform bug: try the same update from Aurena itself and inspect the resulting network calls in the browser's dev tools to see what a working PATCH request actually looks like; try sending only a single changed field (e.g. just Description) rather than the full record to rule out a problem with one specific attribute; try removing the If-Match header from the request, since header handling differences are a common source of this kind of rejected-operation error; and test the exact same PATCH via a general-purpose tool like Postman to compare its generated request against what your own program sends, which often reveals a subtle difference (headers, payload shape, or encoding) that a generic OData client library is introducing.