I've investigated the source code of Assetic. This behavior if for debugging combined scripts and stylesheets. Moving Assetic to non-debug mode makes the code works as expected.
So it is neccessary to use combine=false
each time instead of debug mode.
I don't know why Assetic makes debug files unaccessible from the web (generates one name and produce another).
I'll try to post a bug later.
UPD. combine=false
does not work, because even it is set Assetic produses combined files when dumping and requests files with fileparts (like css/ae13694_data_tables_1.css
instead css/ae13694.css
).
To the history - I've filed a bug for it long ago https://github.com/kriswallsmith/assetic/issues/613