Light cover in boot

Another thing that's gone missing - the past few weeks I could hear a strange rattling noise in the rear left arch. I have found the culprit, does anyone know what I need to pin this back up?

Also I put a light bulb in there and the immobiliser goes crazy….must have a short somewhere?

Could these clips work;

GOLF MK2 & GTI TAILGATE INNER PANEL TRIM CLIPS x 5 801867299 C12 GOLF MK2 & GTI TAILGATE INNER PANEL TRIM CLIPS x 5 801867299 C12 : Amazon.co.uk: Automotive


https://www.justkampers.com/801867299-01c-black-trim-clips-vw-t25-1979-1992-5pk.html

Can't help with the OEM clip but I can advise to buy a couple of bags of these - they come in super handy and would easily sort that out.
https://rover.ebay.com/rover/0/0/0?mpre=https%3A%2F%2Fwww.ebay.co.uk%2Fulk%2Fitm%2F202752338994

…..if your immobiliser is also an alarm and is linked to the boot switch that turns that light on (likely) so that if you had set the alarm and someone opens the boot it goes off - then you need to make sure there is a diode in the wire from the immobiliser to that switch to stop it messing with the ground signal that triggers said alarm.

Trace the wire back to the boot push switch that activates that light- have a look and you might have a extra wire running to it from the front of the car or wherever your immobiliser / alarm is - if you do then try putting a diode on the end and see if that sorts your problem out. A simple cheap IN4007 should work.