With WebCenter Sites 126.96.36.199.0 or later , it is observed that basic assets cache will not get cleared on the target server when published using Mirror Publishing method.
However it works correcly for flex assets and works perfectly fine for basic assets with RealTime Publishing.
There are couple of work arounds suggested by Oracle , please refer to
Oracle Support document “1582522.1” for more information
1. Use RealTime Publishing instead of Mirror Publishing
2. Add a custom code to Mirror publish on the target , to the flush the assets