p38 window regulator/motor

Hi guys i'm new to this forum so hello to everybody.
 I have a 1999 p38 range rover last month the drivers door window regulator started making horrible noises and the window wasnt closing properly and window not set was showing on the dash. I took the door card off and the last 4 teeth of the regulator had been worn/stripped away so I got a new one.After fitting it all has been good until this evening when it made the dreaded noise again and window not set came up again.So once again I took the door card off and to my horror the same 4 teeth have been stripped again.I know that the regulator should last more than a month so what could be causing the problem here could it be the actual cog on the motor thats worn and wearing the teeth on the regulator any help you can give will be great ,I am going to call the supplier that I got the regulator from in the morning to see what they have to say. Please help me before I get shares in qhoever makes regulators.