Sometimes, some pieces, are the kings of both sides in many cases, disappear and never come to be visible during the game. The pieces are only able to move.
What browser are you using and what version of that browser? Also what device?
I believe this is an issue even faced in lichess. It is a pinned issue in lichess’ source code github.com/ornicar/lila/issues/5756
Thank you for your answer. The following is my environment.
OS: iOS14.4(iPhone)
Browser:Safari
I can confirm, even I face the same thing on safari browser with iOS 14.4, but it is rare.