This is not an OpenACS topic, but either NaviServer or PO.
I have never seem such a message before. By googling around, it seems that this this error is quite common on windows systems with various servers [1,2] (nothing special about NaviServer). Do you get this error as well on non-windows machines? Do you see this message on the server or on the client side? What is your browser? Is there a place, where i can see, what this page does? What version of NaviServer are you using?
The configuration option of the config file just provides a default value, which can be changed per request with ns_conn [3]. No need to turn it off in general, one can do this per page. So, an easy "fix" would be to avoid compression just for this page.
-gn
[1] https://appuals.com/how-to-fix-err_content_decoding_failed-error/
[2] https://stackoverflow.com/questions/15112104/how-to-fix-err-content-decoding-failed-when-dynamic-compressing
[3] https://naviserver.sourceforge.io/n/naviserver/files/ns_conn.html#10
