A strange and frustrating problem with my 2008 B6 Wagon:

When I open the tailgate (I do not have auto-tailgate), the MFD always shows the status instantly so I believe the micro-switch in the latch is working properly. However, there can be a delay for the courtesy light in the boot to come on. Though sometimes it is instant on but often it is on after a fraction of a second, a couple of seconds or much longer to the point that I couldn't be bothered to wait any longer.

Any idea what may be the issue? Anywhere should I start checking?