When i download a large file over http proxy the transfer stop and the file don't full download.

Clamav is as default configured to block archives which exceed the configured maximum archive size in order to prevent archive bombs.

You can change this behaviour on "Services > Clamav antivirus".

Change the value of "Max. archive size"
or switch from "Block as virus" to "Do not scan but pass" in order to let exceeded archives pass without scanning.