What is the ruling on differing intentions in congregational prayer?

Question:
The first question: The questioner says: Your Eminence, a group of travelers entered the mosque and found another group praying Maghrib and 'Isha' combined and shortened. They did not catch Maghrib with them, but only caught 'Isha' with them. Question: Is it permissible for the entering group to pray the two rak'ahs of 'Isha' with them, intending them to be Maghrib, and then make up a third rak'ah afterwards, and then pray 'Isha' as a congregation by themselves?

Answer:
The most likely ruling is that they should pray 'Isha' with them, intending it to be Maghrib. When they finish, they stand and complete one rak'ah to complete Maghrib, then they pray 'Isha'. If they pray by themselves, that is sufficient, but it is better to have the congregation... They pray with the congregation, and when the first group finishes the shortened 'Isha', the others stand and complete one rak'ah, because they entered with them intending Maghrib, then they pray 'Isha' afterwards.
Q: Meaning, does differing in intention cause harm?
A: It does not cause harm. No, it does not cause harm. The correct view is that it does not cause harm.