Capital Letters (Players) Disappear

[suttinain]

I run my program using map02.map, actions0.txt, and actions1.txt but the capital letters sometime disappear in rendering.
########
#..@..@#
#...a..#
#..a#@.#
#@.a#..#
#.b....#
########
What could be the problems?

[Troublor]

There may be race conditions between input engines.
It could be that one input engine moves a player to a position that is overridden by another input engine.