Sometimes, when the input is evaluated, a new output is generated and the previous output remains below the new output. This keeps happening every time I evaluate the cell, so I get as many outputs as the number of evaluations. And of course, the old output(s) appear in gray (with some degree of transparency), while the new output appears dark as usual. This happens in some cells only, and I don't know what makes the difference between those having this repetition and those not.
