according to https://wiki.52poke.com/zh-hans/沉重球(道具)
detail
In the second generation and the fourth generation, if the calculated final capture decision value is less than zero, it will be equal to 1 and the capture decision will be continued. So theoretically does not appear can not capture the treasure dream.But in the seventh generation, it may be because the introduction of the beast ball, the final capture judgment can be less than 1, so there is a heavy ball can not capture the treasure dream, such as iron dumbbell [source request].
(google translate)