Depends on what you mean by "putting a foot wrong".
To me he rather repeatedly puts us under more pressure and stops us from playing through pressure by picking the easy way out (poor long balls, playing it out for a throw, super safe pass selection). But that may not be "putting a foot wrong", maybe just him recognising that he's not very good on the ball so he should keep it safe.
So not mistakes as such, but detrimental effect to our overall play.
He isn't a particularly good fit to our style on the ball.
The CBs we have signed is more highly rated on the ball than purely defensively. We've been linked more or less exclusively to very good ball playing centre backs. Tanganga (another one that's limited on the ball) seems to be on his way out, despite being home grown.
RCB has been less of a priority because we have Romero and adequate cover in Sanchez, whereas on the left at had only Davies.
I'm very happy that he's proving himself good enough as a cover player. Longer term I think we'd want a backup player that fits our style of play on the ball as well as defensively. But it's not a priority and we can't do everything in one window.
Fair play to him. He's adapted to Conte's system, makes the most of the qualities he has. He's been playing well and weeded out most of his defensive errors. Done at least as well as could be expected.