It just happens sometimes when your E1 converter has RS-45 on board and your cables are BNC or vice versa. There is an easy way to solve these problems using single type balun 75 120 ohm and rack mount baluns.
Metal casing single port balun
16 ports converter with L9 (DIN1.6/5.6) connectors
Front Mount Coax(75ohm) to RJ45(120ohm) 16 port balun panel with DB68 connector