Hey @vmarko,
Thanks for the advice but we already did all those steps (Cleared cached, purged the directory and disable/reenable minify).
Thanks for your help/confirmation @skarck,
we als confirmed the issue now with multiple of our WordPress sites, the filter still changes the HTML Output but not the filename written into the /cache/minify/ folder.
We are quite certain that the issue/problem was introduced with the latest update, b/c if we jump back to the previous version (manually istalled an older version of the w3 total cache plugin) everything works again as expected.
Thanks for your help,
Andreas