Statistics: Number of Woohoos differes by one between Sims

In a one generation household with two Sims who have only ever woohoo'd with each other, the Sim Stats shows different woohoo counts.

Example : Sim A shows "Woohoo'd 800 times" Sim B shows "Woohoo'd 799 times" or similar off by one number. This happens after save/load, travelling between lots or just playing normally.

Step to reproduce 

1. Create or load a Household with two Sims in a romantic relationship
2. Have them woohoo multiple times (10+)
3. Check Sim Stats - woohoo count matches
4. Save and exit then reload the save 
5. Re check stats - one Sim's count is now off by 1 or more.

Expected Result : Both Sims should show the exact same woohoo count if they've only been intimate with each other.

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