Some UI issues are only obvious after a refresh, when the page catches up and you realize the previous view was stale. You can still capture a HAR if Developer Tools was recording the whole time.
Chrome
Before you start working in the app, open Developer Tools (menu > More Tools > Developer Tools) and select the Network tab.
Check Preserve log. Leave the tools open and keep recording. Do not clear the log.
Use CircleCI as normal.
When a refresh or later load shows that the previous view was wrong, stay on the Network tab and click Export HAR.
Attach the HAR to your support ticket.
You do not need to predict the failure. Preserve log keeps the earlier requests, including the stale page load, so you can export after you notice the mismatch.
HAR files can include cookies and session data. Sanitize the file before sending it.
See Creating HAR files for troubleshooting with Support for more info on HAR files and why they are helpful for Support.