World Championship of Chinese Chess in Munich Germany, Round 9, the last round

I just finished playing in the World Championship of Chinese Chess or Xiangqi in Munich Germany. After having a good result (for me) and being in line to win a prize, I blew it all in the last round with a ridiculous blunder in a position where I had the
advantage, possible a winning advantage, and my opponent was short of time. Here is the game:
P = Pawn or Soldier
C = Cannon
H = Horse or Knight
R = Rook or Chariot
E = Elephant or Bishop or Minister
G = Guard
K = King or General
Red Sam Sloan (USA)
Black Pascal Bieg (Germany)
26 August 2015
1. H2=3 P7+1
2. C8=6 H8+7
3. H8+7 H2+1
4. R9=8 R1=2
5. E7+5 G6+5
6. P7+1 C2+4
7. G4+5 C8+4
8. P1+1 C2+2
9. R1+3 C8-2
10. P3+1 P7+1
11. E5+3 E7+5
12. BE3+5 P1+1
13. R1=2 C8+3
14. R2-1 R9=8
15. R2+7 H7-8
16. H3+4 H8+7
17. H4+6 P3+1
18. P7+1 E5+3
19. E5-3 H7+6
20. C6=1 C2=3
21. R8+8??????? C3+1 checkmate
I cannot believe I made such a terrible move. All I had to do is play R8=7 attacking the cannon and he would have had to defend it or move it away. All those cannon moves by Black in this game were going nowhere, just a waste of time.
I probably had a winning advantage earlier. I should have played 12. Front Elephant back to 5, not BE3+5. Then I allowed him to exchange rooks and cannons allowing him to recover from being behind in development due to his wasted cannon moves.
But why I made a horrible blunder like R8+8 I cannot explain except that in several other games by stronger players I saw equally bad blunders in the last round, except that in those other games the player blundering already had a bad position when he
game the game away.
Sam Sloan

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