error message when you connect to the system

[jd_munoz]

hello
I have the following error message when an agent wants to enter the system in the morning:
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proxy Error

The proxy server Received an invalid response from an upstream server.
The proxy server handle the request not could GET / otrs / index.pl.

Reason: Error reading from remote server

Apache/2.2.15 (CentOS) Server at tics.ucuenca.edu.ec Port 80
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try again after delay entry into the system, that always happens in the morning when you first enter, and then the system improves the speed.

agents are connected via LAN example 172.16.1.68/otrs/index.pl
showing someone what would be the cause of the problem

thanks

[jojo]

please ask you proxy admins