I believe the Bootstrap.css file uses a class of .next by default during the transition of the carousel.
In your style.css, you also use a class of .next that you have set to a width of 40%.
Here’s the code:
.singular .next {
float: right;
width: 40%;
text-align: right;
}
If that is used for something else in the site you will probably want to change the class name, or remove the width:40%.