0 bytes files when caching pages

Lester,

I’ve been using your WP Download plugin for many years but now I’m upgrading the whole website to use SEO, implement cache (W3 Total Cache) and few other upgrades.

However after updating WordPress and adding cache plugin, files seems to have 0 bytes. I already tried to revert the changes by disabling/removing the plugin but error persist.

Do you have any idea on how to fix this issue?
Reference: http://ww.wp.xz.cn/plugins/w3-total-cache/

http://ww.wp.xz.cn/plugins/wp-downloadmanager/