The issue occurs in the Map screen.
When the minimap is opened while your group is moving, and they have equipped weapons that have particles effects on them (fire, cold, corroded etc.), the particles effect will remain displayed on the minimap until closed/reopened.
Steps:
1. Equip/Enchant weapon with bonus DMG to fire/cold/shock. etc so the weapons emit particle effects.
2. Go on any map/dungeon and make your group to move.
3. While the group is moving press "M" to open the minimap.
4. Notice that the particle effects from the weapons will remain displayed on the minimap.
Note that the issue occurs from the other "world" particles (like fire and torches etc.) as well, but it is less noticeable as they are static.
For more details, attachments uploaded here:
https://www.dropbox.com/s/vdpy9bjk4wjdn3p/PoE_v1.03.0524_%5BBUG%5D%5BMinimap%5D%20Particles%20from%20the%20Weapons%20remain%20on%20the%20map%20when%20it%27s%20opened.zip?dl=0
http://i.imgur.com/AnhgMVt.jpg