Offset path not working on this object

I work with digital transfers, and usually I have to apply a fill over the artwork followed by an offset path by -0.005in. Then I delete the outermost stroke and leave the smaller object there.

Something close to the "th" image on here.

But sometimes when I apply the offset path, I don't get that smaller object "inside" the original.

In this case I'm referring to the "u." When I apply the same offset, both objects are basically the same size. 

Is there another measurement I ought to be using? The "u" shapes are smaller than the "th", so I imagine that coould be the issue but I get the same results with the same measurments. :S 

Any ideas would be very much appreciated, I tend to have to manually make the yellow shapes thinner which ruins the workflow here.

Thanks so much!