Final answer:
Charles' refusal to accept settlement attempts like the Newcastle propositions and Heads of Proposals in 1646 created instability in England by exacerbating existing conflicts and divisions.
Step-by-step explanation:
Charles' refusal to accept attempts at settlement like the Newcastle propositions and Heads of Proposals in 1646 created instability in England. These settlement proposals would have allowed for a compromise and potential resolution of the ongoing conflicts between Charles and Parliament. By rejecting these proposals, Charles demonstrated his unwillingness to work with Parliament and find a peaceful solution, further deepening the divisions and tensions in the country.