Issues with new M2-level Error class

I've been playing with the M2-level Error class @d-torrance recently introduced, the goal being to merge it with my own version of it which is used in the Macaulay2Web interface to have pretty error messages.
In the meantime, I've found a few issues which I'll enumerate in this thread.
Let's start with this one: incorrect location (it's fooled by the annoying M2-level errors in robust.m2, which one day should go...)

i1 : a+b
stdio:1:1:(3):[1]: error: no method for binary operator + applied to objects:
            a (of class Symbol)
      +     b (of class Symbol)

i2 : last trap(a+b)

o2 = no method for binary operator + applied to objects:
            a (of class Symbol)
      +     b (of class Symbol)

o2 : Error

i3 : locate oo

o3 = ../../Macaulay2/m2/robust.m2:100:25-100:66

o3 : FilePosition

Start with the M2-level Error class and the robust.m2 path shown in the example; reproduce a+b followed by last trap(a+b), then inspect what locate oo uses to report robust.m2💯25-100:66. Done means the resulting FilePosition points to the original error location rather than the misleading robust.m2 errors.