You're still questioning if the bug exists? I can't tell, using my english skills
The bot can shoot in the sky, that happens when the "vecLastEnemyOrigin -> target -> vecLastEnemyOrigin" loop starts, because the z component of the vecRandom, in BotBodyTarget, is not zero. Am I right? Each bot has a constant skill number, for the remainder of its lifetime. When that loop is in effect, for each frame, it adds that constant vector, set through the BotAimTab vector (index computed using the bot's skill number). As the bot's aim moves, it draws the internal diagonal of a parallelepiped in the space, a diagonal of opposite corners. One of this opposite corners is the true last enemy origin, the other opposite corner has the coordinates of the true last enemy origin plus multiple of vecRandom, which is constant for each bot (because its skill is constant).
LE: actually, it's not a parallelepiped and no straight line is drawn, because vecRandom is not constant, each component is calculated as RANDOM_FLOAT(limit1,limit2). But the z component is not zero (unless it was a random result for that macro, or whatever it is).