Import list of titles or people in the imdb list
This error is thrown by Puppeteer. Unfortunately I'm not familiar with it or Chrome/Chromium browsers. But from what I could find, the problem likely occurred due to network error. Since you provided a range, does it mean that you have tested this multiple times and the error always occurred between adding 400th and 480th movie? If so, then maybe it is some sort of delay introduced by IMDB server due to high server load at the time. In this case, I don't see what I can do besides introducing an additional delay between requests. But this could significantly increase the time it takes for the script to run.
I've tested the script by trying to add over 540 items and there were no problems.
ProtocolError: Runtime.callFunctionOn timed out. Increase the 'protocolTimeout' setting in launch/connect calls for a higher timeout if needed.
I get this error when adding more than 400 to 480 movies to my list