spot on, especially certain mobile fitting companies, the fitters dont care, most dont take the time to install alarms PROPERLY. I fit alarms for myself and i will only fit alarms i know like the back of my hand and know are reliable, clifford's for example are very reliable if installed properly but if not are the most tempremental alarms in the world!!!!
i have removed and binned more cliffords that have gone wrong due to poor fitting,
i refuse to work on cliffords or anyone elses work for that matter unless removing and refitting my own alarm. i generally install Toad or Cobra alarms and have never had a comeback apart from faulty parts!

i know this doesnt help, your case but i thought i'd share!

if the installer has installed to your gems module incorrectly then that will be why ur factory alarm is playing up.