I had a screening call and a technical interview. And for both calls there were serious problems with either network or freezes/delays on the other side, so it was quite uncomfortable. After these I got a coding/machine learning challenge for 3 hours, and they encourage to work on it for several extra days. I find it unrealistic to do this in 3 hours, because there's just too much. Also I find both problems a bit ill-stated (very tricky target and use of sequences when there's no sequence). I don't see many reasons to spend several days(or >3 hours) on these problems, that's just risky in terms of efforts.