[Vestas]

From the manual :

- For rear centre(4) seat
As a reminder to the rear passenger, the rear passenger’s seat belt warning lights will illuminate for approximately 6 seconds each time you turn the ignition switch ON regardless of belt fastening. If the seat belt is not fastened when the ignition switch is turned ON, the seat belt warning light will illuminate for approximately 70 seconds.

 

[Vestas]

Well, that answers that, thank you

It sort of does but doesn't really explain why it does this. The only thing I can think of is that unlike all the other seats the rear middle one doesn't have a weight sensor to detect if anyone is sitting there. That's just a guess from me....