Thank you for the report. Chests are only guaranteed if there is a chest icon on the mini-map in the top right, which will be the first time you clear a boss area ever, so when you change campaigns or to an area further than you've cleared before. After you do a soft-reset, chests only have a chance to drop from a boss you've cleared before the first time you kill them that play through.
 "Crusaders of the Lost Idols"){kind=icon}
 "GemCraft - Chasing Shadows"){kind=icon}
 "Solarmax 2"){kind=icon}
 "Dead Zed 2"){kind=icon}
 "Strand"){kind=icon}
 "Magnetized"){kind=icon}
 "SkullFace"){kind=icon}
 "Death vs Monstars 2"){kind=icon}
 "Dibbles: Pro Pack"){kind=icon}
 "CycloManiacs"){kind=icon}
 "Mastermind: World Conquerer"){kind=icon}
Thank you for the report. Chests are only guaranteed if there is a chest icon on the mini-map in the top right, which will be the first time you clear a boss area ever, so when you change campaigns or to an area further than you've cleared before. After you do a soft-reset, chests only have a chance to drop from a boss you've cleared before the first time you kill them that play through.