Imploding dynamics

Take 3 staves with the same dynamics in the same place in each stave.
When imploding the 3 staves into 1 the dynamics in the imploded stave appear bolder than usual, even after the imploded stave has been imploded again to make all the notes 1 voice. After selecting the dynamic and pressing delete it is still there. Select and delete again and the dynamic is still there but now not bolder.
It appears that the dynamics have been placed in the imploded stave 3 times. Perhaps they are in very very slightly different positions which gives the appearance of one bold one.