As you can see at www.t-innova.com, long testimonials 'cut' the last lines so you cannot see the author nor the [read more] and [show all] options.
I've tried with smaller font, but the problem is the same
Sorry about the issue you are having with Ninjamonials rotator module.
Unfortunately this is a shortcoming of the module and something that we will improve in the next version of the module.
The module was made to handle testimonials of a similar length, and when there are long testimonials, this is a problem.
The only thing you can do for now is to increase the height of the module (in the module parameters).
Another option is to show less testimonials. Show four or five short testimonials and provide the link that takes the users to the testimonials page where they can see all the other testimonials.