This one wasn't as bad as I remember it being (another one I didn't read as a kid). I thought they might hit on the inability to morph clothing a little harder, especially since that's always been Marco's deal and this is his book.
There are a few continuity issues (one in book and one for the series)*, but nothing much to complain about.
Spoilery discussion under the cut.
*While in flea morph Ax and Tobias are on Jake one moment and then on Marco the next. And Ax says something that makes it seem like he's never seen a killer whale before even though David morphed one in The Solution (which by the way, how did he acquire a killer whale?).
I'm not sure about Derek in the book. There were no obvious stereotypes, but I'm not Inuit so I wouldn't recognize anything problematic if it was there. I'm not a huge fan of the description of his "slanted eyes."
The descriptions of everyone getting torn up by the ice are gross but they just suddenly stop about halfway through the book. I'm not going to complain too much, but it is pretty jarring to get a graphic description of a gorilla's body coping (or rather not) with the cold to getting nothing about how awful it would be to demorph from a wet seal's body to a wet human body in the arctic.