Bush MB60, TR82, VTR103 and other variants

[pwdrive]

It depends which way you look at it, to a certain extent with that old plastic stuff it's in the lap of the gods.
If there happens to be the start of a feint hairline crack on the plastic boss then attempting to remove the knob by tension from the front is likely to make the crack worse which could lead to a total fracture, the risks of that are reduced if the knob is removed by compression using a couple of screw drivers from the back.

Lawrence.