Before buying the expensive DeepShredder
13 engine I have visited Jiri Dufek to run several tests.
I have found the following problem.
Lubomir Koblizek, Special hm, Die Schwalbe 2015
1.f7 Rg8 2.fxg8B! Kg1 3.Bg2!.
Every good engine include Shredder
12 is able to find the solution almost immediately.
13 does not.
Generally it is able to see a bishop underpromotion only on the root.
First it completely disqualifies this engine for using in endgame studies.
Second something like we have already seen, did not we