I don't mean the standard error debugging of AMXX. There can be an error within your routine, those things do not necessarily throw an error.
You should add some log_amx to see which events happen and which don't so you see where the problem resides.
For example this will show you which players you cycled through, if one is missing you know where the problem resides and you can attempt to fix it:
PHP Code:
for( i = 0; i < num;i++ )
{
index = players[i]
log_amx( "Player %d", index )
//...
}