ILLEGAL: n c9-d7 on turn 3:
There was no n on c9. The piece on c9 is a q.
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For diagnostic purposes, here is the full movelist:
1. P h2-h4 
1... p h8-h6 
2. P g2-g4 
2... p g8-g6 
3. P e2-e4 
3... n c9-d7 
4. P d2-d3 
4... b i9-e5 
5. B i1-g3 
5... b e5-g3 
6. N f1-g3 
6... p f8-f6 
7. N c1-b3 
7... m d9-c7 
8. M d1-e3 
8... q e9-f8 
9. Q e1-d2 
9... p i8-i7 
10. b1-c1;a1-d1 
10... b h9-b3 
11. P c2-b3 
11... n f9-g7 
12. K c1-b1 
12... n g7-e6 
13. P f2-f4 
13... n e6-c5 
14. P f4-f5 
14... p g6-g5 
15. P h4-h5 
15... r g9-g7 
16. P d3-d4 
16... n c5-b7 
17. R d1-c1 
17... m c7-b6 
18. M e3-c4 
18... k b9-c9; r a9-d9 // O-O-Oc
19. Q d2-c3 
19... m b6-c7 
20. M c4-e6 
20... m c7-b6 
21. M e6-f8 
21... n d7-f8 
22. P e4-e5 
22... r g7-c7 
23. Q c3-b4 
23... r c7-c1 // check!
24. R g1-c1 
24... resign
In case there is a bug in the code, the settings file can be edited at /play/pbm/play.php?game=Pseudo-Modern+Random+Chess&settings=P-MRC&submit=Edit