FileMaker Pro 17
Often I'll bring up the script workspace and click a script in the list, and it fails to display in the detail pane. Sometimes I can work around it by double-clicking the script, or close the script workspace and re-open it.
Not sure how you'd reliably reproduce this, it's sporadic. I do work on files that may contain hundreds of scripts.
This also happens in other schema-related windows. I'll add to this thread next time it does.