Extremely slow connection to linked tables

I have 3 computers with front end databases where the user can choose a
backend data file that is stored on computer A. If any one of the computers
reconnects to the tables it works fine and connects in under 3 seconds.
However, if a user is connected to the backend data file on one computer,
opens any of the forms, and another computer tries to link to the file, they
have to wait up to 10 minutes for the connection. If a third computer
joins, it is even slower.

I have checked the front end and back end so that it opens shared, with no
locking checked. I have also confirmed that the network speed is not an
issue.
Can anyone tell me what I am overlooking or how to avoid this situation?

Thanks in advance.