When piece captures through the last row it remains as a piece and does not become a king. It may flash for moment as a king. This bug ruins compositions, analysis and studies. For example this composition: lidraughts.org/training/russian/14

Oh! The bug happens only if multi-captures on analysis board is set to "All at once".

Indeed, I made a mistake some time ago that caused this bug. Thanks for reporting, I fixed it right away