There are immense internal differences among Chakavian and Kajkavian speeches. Northern Chakavian and Southern Chakvian border on complete unintelligibility. No one argues that there are some ancient (centuries-old) isoglosses that Ča-Kaj share (and there are just as many that Što-Kaj and Što-Ča share as well), but overall degree of mutual intelligibility is very low, apart from some transitional areas in the north. I'll look to find some sources to back up the disputed statements. Personal opinions and experience don't matter on Wikipedia unless they are written in reliable sources.