I had a look at this issue. A JavaScript error does not appear and WP-Piwik itself does not execute any JavaScript there (I assume your problem is related to the widget configuration page?), but WP-Piwik uses jQuery Sparklines to create the toolbar graph… and this seems to cause the issue.
As a workaround, just disable the toolbar graph.
Maybe the Page Builder uses a JavaScript method which is also defined by jQuery Sparklines, so the Sparklines method overwrites the Page Builder method and causes the issue. A hint on this is the warning about a “NaNheight” after changing the row ratio in Page builder.
Sparkline seems not to be maintained any more (https://github.com/gwatts/jquery.sparkline – last authored 2 years ago), so maybe it would be the best solution if the Page Builder team can check this and rename the affected method (if my assumption about the method conflict is correct).
If it’s true Sparklines isn’t supported anymore, I will also check for a replacement, but this will take some time.