I'm not sure if this is a bug or if I'm missing something. Here's an example (wasn't able to reproduce the bug in simpler examples):

```
{ \mu, \nu, \lambda, \kappa, \rho, \sigma# }::Indices(total, position=fixed).
\partial{#}::PartialDerivative.
\nabla{#}::Derivative.
def expand_nabla(ex):
for nabla in ex[r'\nabla']:
nabla.name=r'\partial'
dindex = nabla.indices().__next__()
for arg in nabla.args():
ret:=0;
for index in arg.free_indices():
t2:= @(arg);
if index.parent_rel==sub:
t1:= -\Gamma^{\sigma1}_{@(dindex) @(index)};
t2[index]:= _{\sigma1};
else:
t1:= \Gamma^{@(index)}_{@(dindex) \sigma1};
t2[index]:= ^{\sigma1};
ret += Ex(str(nabla.multiplier)) * t1 * t2
nabla += ret
return ex
ex1:= covd1_{\alpha \rho \sigma} = \nabla_{\alpha}{h_{\rho \sigma}}:
expand_nabla(ex1)
rename_dummies(ex1);
ex2:= covd2_{\lambda \alpha \rho \sigma} = \nabla_{\lambda}{covd1_{\alpha \rho \sigma}}:
expand_nabla(ex2)
rename_dummies(ex2);
substitute(ex2,ex1, repeat = True);
```

There are four terms which require this substitution in the final step. The result seems to actually substitute for three of them but one term doesn't get substituted as in the image below: