Shredder 10 having trouble finding mate in 4

[Uri]

Shredder 10 is having trouble finding mate in 4 while Chessmaster 9000 which is slightly weaker than Shredder 10 finds it easily. Chessmaster is much better than Shredder in finding mates. What could be the reason for this?

[d]8/8/1b6/8/4K3/8/6k1/5q2 b - - 0 72

Analysis by Shredder 10:

1. -+ (-#6): 72...Qb5 73.Kf4 Qd5 74.Kg4 Bd4 75.Kf4
2. -+ (-#8): 72...Qd1 73.Ke5 Qd7 74.Ke4 Qb5 75.Kf4 Qd5 76.Kg4
3. -+ (-#8): 72...Qc4+ 73.Ke5 Bc7+ 74.Kf6 Bd8+ 75.Kg7 Qe6 76.Kf8 Qf6+ 77.Kg8 Qg6+ 78.Kf8 Qh7 79.Ke8 Qe7#

[Mike S.]

Shredder 9 SE doesn't have big problems:

Analysis by Shredder 9 SE (after ~10 seconds at depth 11):

1. -+ (-#4): 72...Qb5 73.Kf4 Qd5 74.Kg4 Be3 75.Kh4 Qg5#
2. -+ (-#6): 72...Qf3+ 73.Ke5 Qc6 74.Kf5 Bd8 75.Kf4 Qd5 76.Ke3
3. -+ (-#7): 72...Qc4+ 73.Kf5 Qc6 74.Ke5 Kg3 75.Kf5 Bd4 76.Kg5 Qf6+ 77.Kh5 Qf7+ 78.Kh6 Be3#

Although, a #4 should be found almost immediatly, nowadays.

Single variation mode (after restarting the engine and without learning file), at D945 3.4 GHz:

Analysis by Shredder 9 SE:

72...Qf6 73.Kd3
-+ (-16.65) Depth: 2/4 00:00:00
(...)
72...Qf7 73.Kd3 Qb3+ 74.Ke4 Qe6+ 75.Kd3 Qe3+ 76.Kc2 Ba5
-+ (-17.18) Depth: 6/16 00:00:00
72...Qb5
-+ (-17.19) Depth: 6/18 00:00:00
72...Qb5 73.Kf4 Bc7+ 74.Ke4 Qc4+ 75.Kf5 Qf7+ 76.Ke4 Qf6
-+ (-17.24) Depth: 6/18 00:00:00
72...Qb5 73.Kf4 Bc7+ 74.Ke4 Qc4+ 75.Kf5 Qf7+ 76.Ke4 Qf4+ 77.Kd5 Kf3
-+ (-17.35) Depth: 7/18 00:00:00 353kN
72...Qc4+
-+ (-17.36) Depth: 7/20 00:00:00 375kN
(...)
72...Qf3+
-+ (-#8) Depth: 9/18 00:00:03 2507kN
72...Qf3+ 73.Ke5 Qc6 74.Kf5 Kf3 75.Kg5 Qe6 76.Kh5 Qg4+ 77.Kh6 Bd4 78.Kh7 Qg7#
-+ (-#7) Depth: 9/18 00:00:03 2594kN
72...Qb5
-+ (-#4) Depth: 9/18 00:00:03 3061kN
72...Qb5
-+ (-#4) Depth: 9/18 00:00:03 3062kN (stops)