W163 remote central locking / alarm

[clk320cabriolet]

Hi all, I have a 2003 ml 400 w163, all was fine then one day about 6 months ago the alarm started to sound at night for no reason, after a few days of doing this, it stopped and has not done it again since, now, since a couple of months, the remote locking has failed, the light on dash still flashes and the button on the centre console works to lock the doors, I would really like to get the remote locking working again so does anyone have any ideas?

can a faulty alarm siren cause the remote locking not to work?

or, can I just add an aftermarket remote locking kit and wire it to the button on the centre console?
many thanks