In real world settings, yes, though it seems that when woman are used to such breasts (especially if they are natural like the model I picked) that moving around poses not that much issues as you would expect.
But as this is a manga/ anime world where the rule of boobs get in the way dont apply..... plus for Stella, she has been adventuring for a good while while having such bombs, including fights, so she would be used to them and able to calculate around them (plus with her gear she could dragonize her chest to remove the weight and such if she really has an issue with them (though I doubt i'll do that as much as it will prevent her to dragonize an other part)