There are different types of ethernet cables - 2 different types of CAT5 as well as CAT6, All use the same connector. It's possible that your 2 cables are different types. The type of cable is usually printed on the cable sleeve.
Also, can the CAT5 cables have issues? I have more than one - one for the studio and one for gigging. Is it possible there is an issue with my cable? Maybe will try to test that out but it will be a pain to run it in the studio.