This comes from other plugins or even from the theme. Please deactivate all plugins and check them one by one to find the one which case this issue. This problem doesn't come from wpForo side.
Is there a possibility to hide the broken icons ?
The theme "ronneby" is not compatible with wpForo. It breaks whole wpForo style and functions. Even menus are crashed. All comes from this css file /wp-content/themes/ronneby/assets/css/app.css
If you want to have wpForo forum on your website I recommend change this theme, we can't help you to solve such large amount issues. You should ask this theme support to make it more intact or just use other theme.