I hope you are having a VSWR meter. Keep the range in 900 band. Then disconnect your cable at the cabinet end n connect VSWR meter.
Normal values has to be 1.4 for VSWR and 1.04 for DTF. If u get a value say 64.5 VSWR it means that the port is opened somewhere. u can also say that the signal which was sent by VSWR meter has not all returned back. Ultimately the job of a VSWR meter is to send a signal n check the value of signal returned and if not, the measure of signal loss, n also the distance where the signal is lost.
if u get a a very high level VSWR, then check the DTF. it will give you the dictance where u have got th problem, u can approximately calculate the distance of cable check at the nearest junction again. this way u can find exactly wher the issue is.
hope u r atleast a bit clear.