Dont know if this helps but here goes, I took the orriginal alarm out of my GTI as the battery pack was knackered and I had no insurance alarm, any way just paid a lot of money and had a Cobra alarm fitted and this works great, however when I lock it the alarm bleeps which is an indication of a fault.
After calling out the alarm engineer and contacting the manufacturer the fault was traced to the interior lamp time delay, this could be rectified with some sort of "diods" (excuse the spelling) being fitted but as the alarm works fine I havent bothered.
this may be of use to you, regards.