Islam critiqued struggling relationship; jealousy always a sin?

In answer to the video "Muhammad's Marital Strife Part 1- Strong Form"

As noted by the earliest scholars the jealousy – of either husband or a co-wife, when it does not lead to transgression either by words or by actions, is not blameworthy.

Here are some practical examples. The prophet had such an intense remembrence of his first wife Khadija that whenever she was mentioned he gave her the best of praises so that Aisha used to say

"I never envied any woman as much as I envied Khadijah. The Holy Prophet always remembered her. Whenever any sheep or goat was slaughtered, the choicest parts were sent to Khadijah's relatives and friends. I used to say, 'It appears that Khadijah was the only woman in the world.' Hearing this, the Holy Prophet was very much annoyed and said: 'Khadijah had many virtues, which others do not have. "'

However such spousal jealousy isnt blameworthy, especially considering how Aisha herself reported Khadija’s merits. There are some documented conflicts and instances of petty jealousies among Prophet Muhammad’s wives, but this was by no means the norm and the prophet was always considerate and delicate when handling these issues. Aisha narrated:

“Once, Sawdah visited us and the Prophet sat down between me and her, one leg in her lap and the other in mine. I made then Khazira (a dish of bran in meat broth) and told her: “Eat!” She refused. I said: “If you don’t eat I will stain your face with Khazira,” but she insisted not to eat; therefore, I put my hand in Khazira and painted her face. Seeing that, the Prophet laughed and gave his share in Khazira to Sawdah and told her to stain my face; so, Sawdah stained my face and the Prophet laughed".

There are many such reported instances of the prophet's tactful handling of tense co-wives situations.
His wives got along amicably otherwise, with mutual respect and sisterly love. Just like normal women, though, they had their human weaknesses and moody phases.