Okay so here's the scenario that's forming in my head:
The MU team was Galz, mcmc, Robz. Robz was, in fact, a 1-shot Tracker, like he said, thus it was a safe claim for him. Maybe he's even a full Tracker, but of course claiming 1-shot that's been used makes him unlikely to be nightkilled. After he lost one partner and looked like losing another, he decided the best thing to do was to claim and say he Tracked mcmc. Maybe he actually tracked me or someone, I don't know. He figured that scum generally want to claim late, so claiming early gives him Town cred, and he can definitely give Town cred to mcmc as well. And of course it worked. Later on the time came to bus mcmc, and so of course he did that, since lynching mcmc is what Town Robz would have done.
Then we get to last night. On the one hand Robz doesn't want to kill ash, because of ash's Town read on him. But maybe he can use that to his advantage. Robz' plan is to make it seem impossible that there can be a third MU, so he can't be critiqued for his interaction with mcmc. But if he argues that, then having ash around is a problem. ash can't be Maquis, so saying there can't be MU left makes ash, plus whoever he investigated an "IC". He was unlikely to investigate Robz because of his Town read on him, so killing liopoil means there will most likely be two confirmed non-Maquis, so Robz arguing that there has to be a Maquis left will put it to a 50/50 between him and either me or yuma. So of course he kills ash. He loses the benefit of having ash around saying he's Town, but he gets the benefit of having a confirmed Town who said he was Town, and someone died who Robz "surely" wouldn't've killed, and he can now go ahead with his "There has to be a Maquis" plan more safely.