Seems the new SFDC update ( Spring 17 ), it is now impossible to update a static resource.
We have a static resource named "res", containing a zip file with following content :
/resource ( folder )
/style/myCss.css
/img/myImage.jpg
etc ....
When we update myCss.css , regenerate the zip file, upload it by editing the static resource, in our lightning community app we still have the previous content of myCss.css ( checked with Chrome inspector )
We tried lots of things :
browser cache delete, change browser, change computer ....
even DELETE myCss.css and reuplaod the static resource,clear cache, and lightning app still contains myCss.css !!!
but the result is always the same.
Once a static resource is loaded the first time in a lightning app inside a community, its initial version is cached and can NOT be updated.