'Festering Grudge' doesn't go away

Me too, I have the same issue.

[My Environment]

• PC version, Windows 11, DX9
• Own all packs
• No Mods

[Affected Sims]

• All life stages, all occult types, regardless of gender.
• Example: A negative sentiment (A) obtained in the infant/toddler stage will still be active. Once Sim (D) ages up, this bug cannot be resolved anymore, since sentiment (A) cannot be intentionally re-added after aging if it was a life-stage specific one.

[Period]

• Since the implementation of the sentiment system, until now.

[Steps to Reproduce (B)]

1. Sim (C) performs any mean interaction on Sim (D), which gives Sim (D) a negative sentiment (A).
2. Without apologizing, let sentiment (A) expire naturally on Sim (D).

[What Happens]

• Sentiment (A) remains hidden on Sim (D) in the background.
• The “Apologize” command remains available from Sim (C) to Sim (D).
• Even if Sim (C) apologizes, it does not clear, because sentiment (A) is already removed from the UI.
• Sim (D) continues to autonomously perform mean interactions toward Sim (C), based on the hidden sentiment (A).

[Workaround 1]

• After (B), manually re-apply the same negative sentiment (A) to Sim (D).
• Have Sim (C) apologize to Sim (D).

The moment the sentiment disappears via apology, the bug resolves.

[Workaround 2]

• Save Sim (D) to My Library, delete them from the world, and then place them again from the Library.
• Since sentiments are not preserved in Library/Gallery saves, this clears it.
• However, all family relationships etc. are reset, so this method is impractical.

[What Happens After Fix]

• The hidden sentiment (A) is truly removed.
• The “Apologize” command disappears.
• Sim (D) no longer performs autonomous mean interactions due to sentiment (A).

This issue is often discussed in the Japanese Sims community.
It has been known for a long time, but I couldn’t find the proper thread until now—thank you for posting it.