Seat Belt rachets

[chris-au-surf]

I have a 94 3.0L surf diesel and the seatbelts in the rear and front passenger seat tend to lock up when trying to put the belt on. If you whip the belt down too fast it locks up as it should but some days even babying it out they lock up. So my 3 questions are:

A: Can these be serviced?
B: Do they need replacing?
C: Is this difficult?

It looks like it may be a nightmare as the panels all need removing. Have any of you guys done this?

Cheers,
Chris.