Calendar Causing Problems Since WordPress Update

Since I updated to WordPress 4.5 (I am now using 4.5.1), using the calendar has been causing my website theme to glitch. I have been in contact with the theme developers and they say it is the calendar. I now have the calendar de-activated, but it is an important part of my site. I had been using it as a widget on the home page. When I activate it, it makes the entire visual of the site change – the menus become a list instead of the way they should be and the theme doesn’t function properly. I have the most updated version of the calendar, theme and WP, so I am not sure what is going on. When I switched from my theme (Dante by Swift Ideas) to Twenty Sixteen, the issue stopped immediately. I am not sure what is going on, but I need this calendar to work.

Thanks

https://ww.wp.xz.cn/plugins/spider-event-calendar/