The lightning bolt button at the top of the screen is a quick link to our quick swap tool. And if it ever turns red and shakes, it means you have players that have since been ruled out in your lineups in your entries file. If you see this button red, you should basically always click it and use the quick swap to quickly remove all out players from your lineups. You never know what exactly might happen, that would prevent you from removing out players later, so you should always get this done as quickly as possible.
From there, you may want to consider also rebuilding your lineups. If it's before lock, you can just start with a fresh build if you have time to rebuild your lineups. If it's after lock, you can run a late swap build to rebuild your lineups, taking advantage of the most up to date sims after that player got ruled out. Check out our late swap tutorial videos for more information about quick swap and late swap. And if you have any other questions about the rest of the lineup building process on SaberSim, check out some of the other videos in our support documentation. In the meantime, thanks and good luck.