Overlapping moving sum need not be Markov

For i.i.d. Bernoulli variables, $K_n=X_{n-1}+X_n$ hides which summand is the newest one. Given $K_n=1$, the previous value can reveal $X_n$ and thereby change the conditional law of $K_{n+1}$, so $(K_n)$ need not be a Markov chain.