I have some issues while testing my clientlibs (configured for proxy). When I tried to use debugclientlibs query parameter, then mostly all the clientlibs are showing 404 status.
I am using AEM 6.4, please let me know if we need any other configuration.
Known issue - CQ-4278585
This regression got introduced as AEM switched to a file system based outputcache.
That flag no longer works as expected.
The resolution for this has been deferred and is not currently in scope to be resolved.
But feel free to log a Daycare ticket -- just be sure to fully justify the business impact this is having in a quantifiable way.