Testimonials not behaving

Hi. I've got the Essential Content Type plug in installed and activated (but the problem holds true even when it isn't)... When I try to add plugins to the homepage, I can't change the number of Testimonials. It defaults to three and anything I do results in "invalid number". That's true if I increase OR decrease the number of testimonials. (The demo mode shows four perfectly and I've got four Testimonials published.) I've got a static homepage but the problem occurs if I set the testimonials for all pages or only for the homepage. Not sure where I can go with this...?