Widgets causing bugs within theme

We have a blog on our main website. However there seems to be a problem with the template. I did not create the template, this was outsourced. I have installed the files on a temporary server to make changes to as I need to get them reviewed because putting the changes on the live site.

I am using the same version of wordpress and also the exact same template files. The template works fine….. until you activate any other plugin apart from the two that are showing at the top (categories , recent posts)

It causes bugs if you activate ANY other widget, wordpress ones or ones that i have installed. The post seems to move frames and also the styling of the sidebar dissapears. I understand this is a bug within the template however would anyone know how to fix this?

This is the temporary site where I am making the changes, you can see how it’s showing:
https://laura-k.com/saleroom-blog/

This is how it should look like:
https://blog.the-saleroom.com/