GLC Alarm System Signal Problem Experience

I had a similar issue with my 2018 BMW 5 series. The alarm system was acting up due to a faulty connection. Did you check the wiring harness and connectors near the alarm controller itself Sometimes water ingress or corrosion can cause signal problems

That's helpful. Where is the alarm controller located on the GLC I haven't had a chance to look yet, and I'd rather not start pulling apart the interior without some idea of where to look. Also, when you mention the wiring harness, what specifically should I be looking for

On the 5 series it was behind the rear panel in the trunk. Check the repair manual for the location in your GLC. By wiring harness, I mean the group of wires bundled together going into the alarm controller. Look for any signs of damage, loose connections, or corrosion. If you aren't comfortable with electrical work, I'd recommend taking it to a workshop. It might save you some headaches.

I appreciate the help. I'll examine the wiring and then bring it to the shop. It turned out to be a corroded connector just like you said. 110€ later, they replaced the connector and did an alarm reset. Everything is working again now.