Explainer-Why has the Iran-US ceasefire memorandum frayed?

Renewed U.S.-Iranian hostilities are eroding an interim ceasefire agreement signed in June, as disagreements over the Strait of Hormuz and unresolved issues like Iran's nuclear program persist. The 14-point Islamabad Memorandum of Understanding, which declared an end to hostilities and open shipping in the Strait, has been criticized for vague wording and leaving key issues for future negotiations.