Network cables are not used in fax, phone lines are. I would guess it is a phone line quality issue if all faxes, and a compatibility issue if always to one specific location.
Try listening to the transmission first:
Machine Status > System Setup > OK > Sound / Volume > OK > Speaker > ON > OK > OK > Stop
Remember where to do that because faxes are one of the most annoying sounds in the world.
The only other thing is to try out ECM (Error Correct mode), it will probably clear the error, but will take longer to send.
Machine Status > Fax Setup > OK > Sending > OK > Error Correct mode (ECM) > ON > OK