We consider KdV-type equations with C 1 nonhomogeneous nonlinearities and small dispersion ε. The first result consists of the conclusion that, in the leading term with respect to ε, the solitary waves in this model interact like KdV solitons. Next, it turned out that there exists a very interesting scenario of instability in which the short-wave soliton remains stable whereas a small long-wave part, generated by perturbations of original equation, turns to be unstable, growing and destroying the leading term. At the same time, such perturbation can eliminate the collision of solitons.