You can view all errors by opening the page in Chrome, hitting the F12 key and then clicking the Console tab. Often the error/filename will be a clue as to the source of the error. If it is not, then mouse hover over the filename on the far right, that will show the full path to the file in a tooltip. The path can just about always be used to determine the source of the error.
After you determined the source, try deactivate the offending plugin.
If the Console doesn’t give you any useful info, you have to temporarily deactivate plugin to see which is causes the issue. If you eliminate other plugins as the source, then it is probably the theme,. In that case you would have to temporarily switch to the default theme to see if the issue goes away.
Hope that helps! Let me know what you find out.