I also have this issue. It’s not noticeable when you play back all layers, so the process still seems to be lossless overall, but for instance I get a nasty buzzing (especially in the HF) that sounds like a noisy guitar amp, on the “Others” layer when separated. It’s cancelled by the sum of other artefacts spread at lower level over other stems. It’s a nasty “gotcha”…
Frustratingly, it’s one of those things that does not always happen.
Mark