Lately when I press the left button on my alarm fob to deactivate it before starting the ignition (standard factory alarm) it clicks rapidly for about 10 seconds, as if the relay is faulty, then stops. The alarm does deactivate just fine, but is this a sign of a problem?

1996 110 300tdi.

Without knowing how the alarm is setup and what they are doing with their circuit it's a little difficult to answer the question with a definitive answer but this rapid clicking of the relay could be down to a number of things. If the circuit is using a voltage rail that is smoothed out with a capacitor that could be faulty. There could be something pulling the rail down such as a faulty component. There could be increased draw due to a fault outside of the circuit. It could be a faulty relay. I don't want to sound unhelpful so I mentioned a number of possible things first but it's a bit like saying my cars power is down, why would that be? If it were my alarm I would try and trace a circuit diagram and take the alarm ECU out to look at it. Is there any water ingress? Are there any bad joints? I would check the voltage levels. Unsolder and check the relay out of the circuit then put it back or replace it.