He pauses for a moment so he can listen, before he frowns. He's definitely not that knowledgable when it comes to fixing the TARDIS but it doesn't seem quite right. "Something sounds... off."

"Hm." He turns to look at the TARDIS console, considering. He turns back to Missy and he can see she's tired so he nods. "I think you're right. Okay, let's reboot her." He moves closer to the console to do exactly that.

He turns to Missy, appalled. "I can do TARDIS maintenance perfectly well. She just doesn't like to cooperate with me."