Well, that only sort of is a bug. I wanted the player to be moved together with the moving platforms but this wasn't the case by default. So I parented the player to the moving platforms when the player is on top of them, but that caused the physics to not correctly work while being on the moving platforms. To make it short: I just disabled the player to move horizontally when on top of these platforms. Don't worry, I designed the game with this in mind and it's still doable. When holding the keys to walk/run forward and then jumping, the jump still gets accelerated forwards. If I manage to fix this issue, I'll do so in an update.