I wonder why did they change the lamb's head features, it looks worse (the expression) after the restoration IMO and such a significant alteration is not acceptable IMO.
It actually seems like they restored it to its original style. It was painted over to make the sheep look more sheep-like. The "new" restored version is actually how the Van Eycks painted it.[0]
[0]: https://www.bbc.com/culture/article/20200201-is-this-the-fir...