ILLEGAL: Q e1-b4 on turn 4:
There was no Q on e1. The piece on e1 is a K.
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For diagnostic purposes, here is the full movelist:
1. e2-e4 
1... h7-h6 
2. P d2-d4 
2... g8-h7 
3. N h1-g3 
3... e7-e6 
4. Q e1-b4 // Check
4... d8-e7 
5. Q b4-b7 // QxP
5... b8-c6 
6. Q b7-c7 // QxP
6... c6-b5 
7. N c1-d3 
7... b5-c7 
8. resign
In case there is a bug in the code, the settings file can be edited at /play/pbm/play.php?game=Janus+Chess&settings=JanusChess&submit=Edit