Two likely explanations:
- changing the number of learning steps while cards are already in learning can result in skipped or repeated steps
- if cards were changed on multiple devices before syncing, you can end up reverting them to an earlier state
To avoid the latter, please make sure you always sync at the start and end of each session: https://www.youtube.com/watch?v=YkiM4DPzSVc&list=PLGgmaKOIHykFoomqkBJAyGiDQ2kyiuTao&index=1&t=224s#syncing-at-start-and-end