You can see that in Snuff as well. The book was....weird. Disjointed in strange ways, not as fluid as the other books were.
[snipped]
I agree with you on this (and I also agree it was still good), and there's a rather specific reason for why -I personally- think Snuff was a bit weird:
The characters started doing monologues to a much bigger degree than usual.
It seems like a strange thing to complain about, but if we go back to
The Fifth Elephant's description of knockermen, it's one of the most powerful description sequences that Pratchett's ever written. I've gotten goosebumps from reading it, it's that good. I could feel being in the cave, being alone, being in great danger, imagining hearing the knocks of Agi Hammerthief...
And here's the thing: Although technically Cheery was explaining to Vimes about all of this, we didn't see her making a monologue about it. Instead it was presented more as if we were reading Vimes' thoughts once he'd understood the entire explanation. Or perhaps how we would understand it after getting the explanation. And then once the main explanation stops, only then do Vimes and Cheery start talking about some details, and even if Cheery's still explaining, it's a proper dialogue kind of talking, which is how the talking should be.
But in Snuff, we're getting characters -especially Willikins the butler- explaining things directly to Vimes in monologues, but with roughly the same tone that the knockermen was described... But it just doesn't work the same. It disrupts the fluidity. And in the case of Willikins, it forced upon him a change of character that felt... well, out of character.
And this tendency carried over even more in Raising Steam, which erased the character of the characters, as they were all doing the same type of explaining monologuing in the same polite manner.