Nobody has mentioned Mate scores yet
I suppose this is more or less correct, but I was a bit worried because in Multi PV Rainbow Serpent somehow lost track of Bc5 as one of the winning moves. Somehow move was either not checked (very bad) or did not Fail High (still bad). Very strange. It must be some kind of bug but I do not know if it is a Rainbow Serpent bug. Because the starter also mentioned Bc5, I am not sure it is purely Rainbow Serpent here or I have to revert Fail High re-searches in PV nodes as most likely culprit. But it shouldn't have this effect.
[D]5R1b/5pk1/6p1/1K2P1P1/3B1P2/r7/8/8 w - -
Engine: Sf20150607_003 MOD MP (512 MB)
by Tord Romstad, Marco Costalba and Joona Kiiski
53 127:33 +M23 1.Rxh8 Kxh8 2.e6+ Kg8 3.e7 Ra8 4.Bf6 Rc8
5.Kb6 Re8 6.Kb7 Kh7 7.Kc7 Ra8 8.Bd4 f6
9.Kd7 fxg5 10.fxg5 Rb8 11.e8Q Rd8+
12.Ke7 Rxe8+ 13.Kxe8 Kg8 14.Bc5 (35.805.619.209) 4678
53 127:33 +M24 1.Rc8 Kh7 2.Rxh8+ Kxh8 3.e6+ Kg8
4.e7 Ra8 5.Bf6 Rc8 6.Kb6 Re8 7.Kb7 Kh7
8.Kc7 Ra8 9.Bd4 f6 10.Kd7 fxg5
11.fxg5 Rb8 12.e8Q Rd8+ 13.Ke7 Rxe8+
14.Kxe8 (35.805.619.209) 4678
53 127:33 +M24 1.Re8 Kh7 2.Rxh8+ Kxh8 3.e6+ Kg8
4.e7 Ra8 5.Bf6 Rc8 6.Kb6 Re8 7.Kb7 Kh7
8.Kc7 Ra8 9.Bd4 f6 10.Kd7 fxg5
11.fxg5 Rb8 12.e8Q Rd8+ 13.Ke7 Rxe8+
14.Kxe8 (35.805.619.209) 4678
53 127:33 +M24 1.Rd8 Kh7 2.Rxh8+ Kxh8 3.e6+ Kg8
4.e7 Ra8 5.Bf6 Rc8 6.Kb6 Re8 7.Kb7 Kh7
8.Kc7 Ra8 9.Bd4 f6 10.Kd7 fxg5
11.fxg5 Rb8 12.e8Q Rd8+ 13.Ke7 Rxe8+
14.Kxe8 (35.805.619.209) 4678
52 127:33 +39.46 1.Bc5 Rb3+ 2.Kc6 Rc3 3.Rc8 Kh7 4.Kd7 Bg7
5.Bd6 Rf3 6.Rc7 Kg8 7.Ra7 Rf1 8.Ke8 Rxf4
9.e6 Re4 10.e7 Bf8 11.Kd7 Bxe7
12.Bxe7 f5 (35.805.619.209) 4678
52 127:33 +1.74 1.Kc6 Ra6+ 2.Kb7 Kxf8 3.Bc5+ Ke8
4.Kxa6 Kd7 5.Kb7 Bg7 6.Bb4 Bh8 7.Bc3 Ke6
8.Kc7 Ke7 9.Bb4+ Ke8 10.Kc6 Bg7
11.Bd6 Kd8 12.Bc5 Ke8 13.Bb4 Kd8
14.Kb7 (35.805.619.209) 4678
A little bit earlier 1. Bc5 had a score of 45.30 and it definitely should not happen that the score falls below that in a next iteration.