The problem is that sometimes the testimonials run into each other until you resize the screen.
Solution:
Add this in Theme Options > Custom CSS:
.slides li {
-webkit-transition: all 0s ease-in-out 0s!important;
-moz-transition: all 0s ease-in-out 0s!important;
-o-transition: all 0s ease-in-out 0s!important;
-ms-transition: all 0s ease-in-out 0s!important;
transition: all 0s ease-in-out 0s!important;
}