Dog,
I don't have the mitre fence in question, but the standard cure-all for this problem is a centre punch and an 'ammer. Apply liberal quantities of centre punch dimples to the sides of the mitre fence bar; this gives the effect of widening same where the metal mushrooms out from the dimple. Obvious when you see it, but not so easy to describe. Hope that might help your situation.
Cheers, Alf