Consider the following example:

```
\m::LaTeXForm("\mu").
\n::LaTeXForm("\nu").
D{#}::Derivative;
{\m,\n}::Indices(s,position=fixed);
{\mu,\nu}::Indices(p,position=fixed);
{x_\mu}::Coordinate;
ex:=D_{x_\mu}{\theta_\mu};
for i in ex.top().free_indices():
display(i);
{x_\m}::Coordinate;
ex:=D_{x_\m}{\theta_\m};
for i in ex.top().free_indices():
display(i);
```

One would expect no free indices in both expressions. Indeed, for D*{x*\mu}{\theta_\mu}, there are no free indices. However, for the expression involving the user-defined LaTeXForm symbols \m, there are free indices.

This creates issues when trying to add two expressions like this together.