After 26...Bc6 Black's bishop is placed well and perhaps it is time for White to settle for a draw. White will risk losing if he overrates his position and insists that he has still an advantage

52 Bxd5? is an error if we consider that in a queen and pawn ending the most important thing to have is a passed pawn

Bingo! I doubt if GM Matlakov would have made that error if he had attended Botvinnik's school, which of course Kramnik did. Botvinnik must certainly have taught his students about this, Kramnik included.

This is another example of an endgame where a present-day active chess master apparently overlooks a basic endgame rule. Adjournment or no adjournment, I am under the impression that present day competitive chess players do not study endgames as much as past ones did.

<RookFile: Well, it's a classic rule in queen and pawn endings that you can let material go if you can push a passed pawn like this. Lasker and Capa certainly knew about this>

I can't quite recall a Lasker Queen endgame where he demonstrates this rule. It would be nice if you can provide links.

Capablanca certainly knew this rule and moreover demonstrates a profound understanding of when and when not to apply it.

See J Bernstein vs Capablanca, 1915

Capa purposefully creates a passed pawn but then refrains from pushing it too far prematurely so that it can act as cover for his King in order to avoid perpetual checks. The game above is one of the most profound Queen endings I have ever played through in the application of the passed pawn rule in Queen endings, demonstrating when to push the passed pawn and when to avoid doing so.

Lisitsin vs Capablanca, 1935

In the next game, Capablanca again demonstrates the passed pawn rule. Against one of the leading Soviet masters of that time, Capa conjures a win out of thin air by immediately creating a Kingside majority and consequently an outside passed pawn in a Queen ending, when his opponent allows him to. While he gives the impression of knowing exactly what to do Lisitsin at times does not seem to be aware of what is happening.

You might have forgotten that Alekhine knew about this rule too.

Keres vs Alekhine, 1936

In this little known endgame clash between giants, Alekhine purposefully pushes his Kingside majority in order to create a passed pawn, all the while never letting go of the initiative by harrying Keres' King, and avoiding perpetual checks. Paul the Great had to concede defeat in the end.

In brief, the general rules in winning Queen endings are: one, create a passed pawn; two, maintain the initiative; three, avoid perpetuals. Of course most Queen endings are still objectively drawish and do end in draws, but if one wants to win, following these rules is the way to optimize playing for a victory.

G Neumann vs Paulsen, 1870