nginx try file, if not found, fallback to rewrite not working (redirection loop)

I have 2 scenarios:

• /media/cache/test.jpg or stylesheet/theme/xxxx.css is generated by the application. It's not a static file present on the filesystem.

• /assets/test.jpg is a static file present on the host

I want both of them to be cached by the browser adding expires 6M header.

So I did:

location / {
    try_files $uri @rewriteapp;
}

location @rewriteapp {
     rewrite ^(.*)$ /index.php/$1 last;
}

location ~ ^/(index)\.php(/|$) {
    fastcgi_pass unix...;
    internal;
}

location ~ \.php$ {
    return 404;
}

# assets, media
location ~* \.(?:css(\.map)?|js(\.map)?|jpe?g|png|gif)$ {
    expires 6M;
    access_log off;

    # try accessing the file directly, and if not found 
    # it means the application has to generate it, 
    # so reroute to the @rewriteapp rule.
    try_files $uri @rewriteapp;
}

Problem is nginx detects a loop:

*194369 rewrite or internal redirection cycle while redirect to named location "@rewriteapp", client: 127.0.0.1, server: , request: "GET /stylesheet/theme/3441-1484735061.css

What am I missing please ?