DFS Replication issues - how to troubleshoot?

I got some problems with our DFS setup with replication and I am looking for someone who can atleast tell me where to get started as I do not have an incredible amoint of knowledge in DFS. What we have is 2 servers that are used in DFS - Domain user and Domain user1. These servers has the files that lab classrooms use. We use DFS as redundancy measure so if one server goes down the labs are not messed up. The problems comes 2-3 days ago when a supervisor updated one of the lab files and then when the lab users would log in half would see the updated file and the other half would see the old file, obviously this was because some were seeing the server with the updated file and the rest were seeing the server with the old one that has not been replicated to. User is the one that contains the updated file, user2 is the one that contains the old file which has not been replicated too. This event log of user2 is not eventful but the event log for DFS Replication on user is very eventful. There are tons of errors with even ID 5002 and source DFSR that you can check below:

Event Type: Error
Event Source: DFSR
Event Category: None
Event ID: 5002
Date: 3/14/2007
Time: 2:51:52 PM
User: N/A
Computer: DOMAIN-USER
Description:
The DFS Replication service encountered an error communicating with partner DOMAIN-USER2 for replication group domain.dept.school.edu\dfsroot\labfiles.

Partner DNS address: domain-user2.domain.dept.school.edu

Optional data if available:
Partner WINS Address: domain-user2
Partner IP Address: xx.xx.xx.xx

The service will retry the connection periodically.

Additional Information:
Error: 1753 (There are no more endpoints available from the endpoint mapper.)
Connection ID: 8218AF8D-3AF5-449B-934E-B6407823122E
Replication Group ID: F0B02BF5-2F04-4F0E-9F81-0BEFB6497F25