Are the drum loops originally from digitakt or you actually create them in logic? Are you using the digitakt metronome as a point of reference? Even set to the same bpm, you probably can’t expect 2 independent devices to have a mathematically perfect synchronicity, therefore if you’re getting something that seems slightly off grid it either is off grid, or perhaps the transients on some hits are longer than the slice segment.
This is just my first thought, it’s definitely possible something else in the conversion is causing it to not cut at the zero-crossing. It’s also my understanding that the stereo samples also make it harder to achieve a zero-crossing slice as well.