shock sensor on the fritz! Help please!

Hi guys, I bought a nobody alarm off of ebay, cause I don't rely on alarms, I just buy them for the pager option. After installing it, it worked fine, except  for that  the first two weeks, almost every other time the alarm was active, the shock sensor would sound its' warning beeps from the siren and pager for about a minute, displaying that the car had an impact, no matter how sensative or de-sensative the shock module was set at. After a couple weeks it stopped and worked great, but about four months later now it is going off every 3 hours (which reaaaaalllly sucks overnight!!!!!), but again just the warning beeps- which are still loud.

Any ideas?

Thanks