So long as they all have a manually assigned, and unique player number, that won't be the issue, but possibly one of the following:
- the router / hub / switch connecting the players
- the ethernet cable connecting that player
- the ethernet jack on the player itself (possibly a bent pin or bad connection)
- some other internal fault on the player
If you check the port and it appears fine, and you use a known-good cable directly between two players, do you still have issues?