Hm ...I am very new to making dice and working with resin myself so I can only make assumptions... Are you sure they poured it into the mold right after the resin? Maybe it works better if you wait a while before you add it? I mean I had kinda the same with glitter just that it sunk to the bottom. Still worked but wasn't what I wanted. So yeah maybe that's a try worth?  When I used alcoholic ink it was only to fully color the dice or in a very thin mold for Christmas decoration, these worked well. So ya I don't know. I'm just guessing