Redmine

There is a problem with task attachment opening:
when working through the proxy (squid) - I have and "Zero size reply"

But in the log production.log I can see that is all "OK" with senidng attachment file:
[ruby@mail redmine-3.3.3]$ tail /opt/redmine-3.3.3/log/production.log -f
Parameters: {"id"=>"15", "filename"=>"!1111111.png"}
Current user: admin (id=1)
Sent file /opt/redmine-3.3.3/files/2017/06/170627050716_fd10e9bb8c8a02820e178817bd8c0f79.png (0.1ms)
Completed 200 OK in 13ms (ActiveRecord: 2.8ms)
Started GET "/attachments/download/15/!1111111.png" for 95.67.17.36 at 2017-06-27 05:07:39 -0400
Processing by AttachmentsController#download as HTML
Parameters: {"id"=>"15", "filename"=>"!1111111.png"}
Current user: admin (id=1)
Sent file /opt/redmine-3.3.3/files/2017/06/170627050716_fd10e9bb8c8a02820e178817bd8c0f79.png (0.1ms)
Completed 200 OK in 17ms (ActiveRecord: 6.5ms)

If I work with Redmine without proxy, I just have browser message "Can not display this page".

System info:

Redmine 3.3.3.stable
Default administrator account changed
File repository writable
Plugin assets directory writable (./public/plugin_assets)
RMagick available (optional)
ImageMagick convert available (optional)

Environment:
Redmine version 3.3.3.stable
Ruby version 2.2.3-p173 (2015-08-18) [x86_64-linux]
Rails version 4.2.7.1
Environment production
Database adapter Mysql2
SCM:
Subversion 1.7.14
Darcs 2.8.4
Git 1.8.3.1
Filesystem
Redmine plugins:
redmine_timesheet_plugin 0.7.0