The code below produces a result where the first fraction (which is half) appears as 12. Any idea why this is happening?
ex := A_{\alpha} \Gamma^{\alpha}_{\beta \gamma} .
substitute(_, $ \Gamma^{\alpha?}_{\beta? \gamma?} -> \frac{1}{2} \Gamma^{\alpha?}_{\beta? \gamma?} + \frac{1}{2} \Gamma^{\alpha?}_{\gamma? \beta?} $ );