We've been experiencing stories that disappear from the Scrum boards we use for a number of projects. It always happens to stories that are carried over from the previous sprint, so they are assigned two sprints (one completed, one active).
When changing the story's status (e.g. from 'in progress' to 'review') it suddenly disappears from the board. It is then visible at the bottom of the backlog.
Changing the status (or one of the other fields) usually brings the story back to the board.
I've tried reindexing the concerning project (as per Atlassian recommendation, https://confluence.atlassian.com/jirakb/issues-are-not-appearing-in-boards-779159013.html), but to no avail. I've verified the issue is showing up in the board query.
The workflow hasn't been changed in about a year, yet this issue started happening some weeks ago. We're using Jira V8.2.1.
Does anyone know why this happens, or what I can do to resolve the issue?