Rear centre inertia unit

The middle belt in the back of my 3 dr 2003 is U/S - locked quite tight and won't release with the usual wiggling.

I've not tried taking the unit out yet as I haven't got hold of the required star(?) bits to take it off, but just wondered if anyone else has worked with these and whether taking it off and fiddling will do any good or it's best just to replace?

It's a seat belt! It's faulty! and someones life is going to rely on it been 100% ok. what do you think you should do with it?