There's a very strange behaviour that's been introduced in pre7 (for missiles) and now for pre8 for melee attacks as well. Monsters will, occasionally, for no apparent reason, become neutral to the PC. Sometimes they'll wander away for maybe 1 turn or so, then come back and attack you again. This in itself isn't that much of a problem, except that it means the player is constantly bombarded with "Do you want to attack the -foo- prompts?" in the middle of battle. Worse, if the player does decide to attack the monster (who was just attacking them a moment before and will continue to do so a moment later), they'll take an alignment hit.

This is very unintuitive and annoying, IMHO.