BUG: Sim feels betrayed with no good reason

Problem
My Sim is suddenly accusing his partner of cheating although they have done nothing wrong. The end of the relationship is not far off.

Cause 
The new reputation system is counting old lovers as cheating as well. If you have any Sims that still show the heart in the relationship panel are counted as cheating on your partner. Also it's not possible to have hidden affairs. If you flirt with another Sim, everybody knows it (even if you do it in the privacy of your own home) and your relationship will go down the drain very fast.

Prevention
Before going steady make sure that you don't have any open relationships showing. Make sure to ask them just to be friends.

Solution
Buy the lifetime rewards Above Reproach and Clean Slate. The lifetime reward No Jealousy doesn't help in this case for it has no influence on the reputations system.

Mods that help with the problem

• Romantic Reputation Recombobulator replaces the system with an new one. You can read about the details in the mods description.