Test Position

[muxecoid]

[d] 8/5n2/2p1k3/8/pp6/2p1PR2/PpP2PP1/1K6 w - -
Stockfish and Firebird need only 5 sec to solve it on my computer.

With simple edit it becomes much harder and cofuses Firebird:
[d]8/5n2/2p5/5k2/pp6/2p1P1R1/PpP2PP1/1K6 w - -

[bob]

I assume you are talking about the time to find Rxf7+? Takes 2 secs on my 8-core box, but takes 17 secs for the score to pass +1.0 and 23 secs to get past +2.0

[PawnStormZ]

  Fire 1.31 does find it both ways here, though not as fast as Stockfish in the 2nd position...

[+2.63] d=27 1.Rf3 Ke6 2.Rxf7 Kxf7 3.a3 bxa3 4.g4 c5 5.Ka2 Ke6 6.g5 Ke5 7.f4 Kf5 8.e4 Kg6 9.Kb1 c4 10.Ka2 Kh5 11.Kb1 Kg6 (0:03.14) 1976031kN

[+1.73] d=27 1.Rf3 Ke6 2.Rxf7 Kxf7 3.a3 bxa3 4.g4 c5 5.Ka2 Kf6 6.f4 c4 7.e4 Kg6 8.e5 Kh7 9.f5 Kg8 10.e6 Kf8 11.g5 b1R 12.Kxb1 (0:02.28) 1478158kN

[+1.13] d=27 1.Rf3 Ke6 2.Rxf7 Kxf7 3.a3 bxa3 4.g4 c5 5.Ka2 Ke7 6.f4 Ke6 7.g5 Kf5 8.e4 Kg6 9.Kb1 Kf7 10.f5 c4 11.f6 a2 12.Kxa2 Ke6 13.Kb1 Kf7 14.Ka2 (0:01.54) 1118710kN

[+0.73] d=27 1.Rf3 Ke6 2.Rxf7 Kxf7 3.a3 bxa3 4.g4 c5 5.Ka2 Kf6 6.f4 Kf7 7.g5 Kg7 8.e4 Kg6 9.Kb1 c4 10.Ka2 Kg7 11.f5 Kf7 12.Kb1 Kg7 13.g6 Kf6 14.Ka2 Kg7 15.Kb1 (0:01.01) 500078kN

[+0.46] d=27 1.Rf3 Ke6 2.Rxf7 Kxf7 3.a3 bxa3 4.g4 Kg7 5.e4 Kf6 6.f4 Kf7 7.g5 Kg6 8.Ka2 c5 9.Kb1 c4 10.Ka2 Kf7 11.f5 Ke7 12.Kb1 Kf7 13.g6 Kf6 14.Ka2 Kg7 15.Kb1 Kf6 (0:00.42) 294001kN

[+0.28] d=27 1.Rf3 Ke6 2.Rxf7 Kxf7 3.a3 bxa3 4.g4 c5 5.Ka2 Kf6 6.f4 Ke6 7.g5 Kf5 8.e4 Kg6 9.Kb1 c4 10.Ka2 Kh5 11.Kb1 Kg6 (0:00.36) 245138kN

[+0.16] d=27 1.Rf3 Ke6 2.Rf4 c5 3.f3 Nd6 4.Rh4 Nb5 5.Rh6 Kd5 6.Rh5 Kc4 7.Rh4 Kd5 8.e4 Kd4 (0:00.32) 216575kN

[+0.08] d=27 1.Rf3 Ke6 2.Rf4 c5 3.f3 Nd6 4.Rh4 Nb5 5.Rh6 Kd5 6.Rh5 Kc4 7.Rh4 Kd5 8.e4 Kd4 (0:00.29) 194732kN

[+0.00] d=27 1.e4 Ke6 2.Rg6 Kd7 3.Rg7 Ke6 4.Rg6 (0:00.18) 116775kN

[+0.00] d=26 1.e4 Ke6 2.Rg6 Kd7 3.Rg7 Ke6 4.Rg6 (0:00.13) 81516kN

[+0.00] d=25 1.e4 Ke6 2.Rg6 Kd7 3.Rg7 Ke6 4.Rg6 (0:00.11) 69767kN

[+0.00] d=24 1.e4 Ke6 2.Rg6 Kd7 3.Rg7 Ke6 4.Rg6 (0:00.08) 52812kN

[+0.00] d=23 1.e4 Ke6 2.Rg6 Kd7 3.Rg7 Ke6 4.Rg6 (0:00.06) 41704kN

[+0.00] d=22 1.e4 Ke6 2.Rg6 Kd7 3.Rg7 Ke6 4.Rg6 (0:00.05) 34190kN

[+0.00] d=21 1.e4 Ke6 2.Rg6 Kd7 3.Rg7 Ke6 4.Rg6 (0:00.04) 27251kN

[+0.00] d=20 1.e4 Ke6 2.Rg6 Kd7 3.Rg7 Ke6 4.Rg6 (0:00.04) 24398kN

[+0.00] d=19 1.e4 Ke5 2.Rg6 c5 3.f4 Kxe4 4.Rf6 Nd8 5.g3 Kd5 6.Rf5 Kc4 7.Rf6 Kd5 (0:00.03) 19249kN

[+0.00] d=18 1.e4 Ke5 2.Rg6 c5 3.f4 Kxe4 4.Rf6 Nd8 5.g3 Kd5 6.Rf5 Kc4 7.Rf6 Kd5 (0:00.02) 15906kN

[+0.00] d=17 1.e4 Ke5 2.Rg6 c5 3.f4 Kxe4 4.Rf6 Nd8 5.g3 Kd5 6.Rf5 Kc4 7.Rf6 Kd5 (0:00.02) 13625kN

[+0.40] d=13 1.e4 Ke5 2.Rg6 c5 3.f3 Kd4 4.f4 Kxe4 5.Rf6 Nd8 6.g4 b3 7.cxb3 axb3 8.axb3 Nb7 9.f5 Na5 10.Rb6 c4 11.Re6 Kd3 12.Rd6 Ke4 (0:00.00) 2060kN

[bob]

For the second position, takes 1:20 to fail high with an initial eval of +1.26. After another minute eval is up to +2.0