ILLEGAL: M f1-g3 on turn 3:
There was no M on f1. The piece on f1 is a N.
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For diagnostic purposes, here is the full movelist:
1. P e2-e4 
1... p e8-e6 
2. P d2-d4 
2... p d8-d6 
3. M f1-g3 
3... n g9-f7 
4. P c2-c3 
4... p c8-c6 
5. N g1-h3 
5... b e9-c7 
6. P f2-f4 
6... m f9-g7 
7. B b1-d3 
7... n c9-e8 
8. N c1-e2 
8... p e6-e5 
9. P f4-f5 
9... n e8-f6 
10. B e1-d2 
10... b b9-d7 
11. M g3-i4 
11... b d7-e8 
12. N h3-g5 
12... n f7-h6 
13. M i4-h3 
13... n h6-g4 
14. N g5-e6 
14... b e8-i4 
15. N e6-g7 //Check!
15... p f8-g7 
16. M h3-g1 
16... n g4-i3; h2-i3; q d9-h5; g1-h2; n f6-g4 
17. g4-f6; h2-h3 
17... b i4-h3 
18. P i2-h3 
18... b c7-d8 
// http://www.chessvariants.org/index/msdisplay.php?itemid=MSkoreanrandomch
19. N e2-g3 
19... q h5-d1 
20. R a1-d1 
20... r a9-e9 
21. K h1-h2 
21... k h9-g9; r i9-f9 // O-O-Og
22. N g3-e2 
22... p e5-d4 
23. P c3-d4 
23... n f6-e4 
24. B d2-f4 
24... n e4-f2 
25. B f4-d6 
25... k g9-h9 
26. R d1-d2 
26... n f2-d3 
27. N e2-g3 
27... n d3-e1 
28. B d6-b8 
28... b d8-g5 
29. R d2-d1 
29... n e1-c2 
30. N g3-i4 
30... b g5-f6 
31. B b8-a7 
31... r e9-e2 
32. R i1-f1 
32... n c2-e3 
33. K h2-h1 
33... n e3-d1 
34. R f1-d1 
34... r e2-b2 
35. P a2-a3 
35... b f6-i3 
36. P g2-g4 
36... r f9-e9 
37. N i4-g3 
37... r e9-e3 
38. N g3-i2 
38... r e3-h3 // check!
39. resign
In case there is a bug in the code, the settings file can be edited at /play/pbm/play.php?game=Chess8400&settings=Main&submit=Edit