I am seeing Unattributable JavaScript execution time. How can I determine what is causing the issue? screenshot
I have tested by removing third party scripts but that didn't help. Not sure what is causing the Unattributable JavaScript execution time.
Unattributable means that PSI can't determine what triggered the JavaScript that was running (the screenshot doesn't give any context, so I'm just assuming this was unattributable javascript and not layout, painting, etc triggered by javascript).
At that point it might make sense to turn to the other audits available in the report rather than focusing on this one. Alternatively, you could try to see if removing first-party code helps to narrow down the root cause of this time.
There's not much more advice that can be given without a URL to test or more information than just that single line from the PSI report.