[OPEN] Sims can't become soulmates

Product: The Sims 4
Platform:PC
Which language are you playing the game in? English
How often does the bug occur? It's only happened when playing my sim paired with Darrel Charm. I have multiple save files with her, and she's been able to become soulmates with the NPC Caleb Vator as well as the CC Geralt of Rivia without issue. I even tested in the save file she's married to Darrel on to see if it was an issue with that save, but she's been able to soulmate with others in that save. It seems to be directly related to Darrel.
What is your current game version number? I'm not sure how to find that? I just purchased the game this month, and it's completely up to date.
What expansions, game packs, and stuff packs do you have installed? Deluxe, Island Living, City Living, Cottage Living, Get Together, Seasons, Parenthood, Dine out, Realm of Magic, Vampires, Kids Room, Toddler, Bowling Night, Movie Hangout, Perfect Patio, Tiny Living, Cool Kitchen, Luxury Party, Paranormal, Romantic Garden, Spooky, Vintage Glamour, Industrial Loft
Steps: How can we find the bug ourselves? Build up a relationship with Darrel, when the game offers the choice "convince to leave" tell it to do that, keep building the relationship and marry Darrel. 
What happens when the bug occurs? Darrel and Vendra don't become soul mates.
What do you expect to see? Darrel and Vendra becoming soul mates.
Have you installed any customization with the game, e.g. Custom Content or Mods? Custom Content - I installed a Geralt of Rivia sim.
Did this issue appear after a specific patch or change you made to your system? No.

One sim is made by me in the CAS, the other is an NPC sim (Darrel Charm).
I built their relationship up naturally, rather than using the available cheat codes.
The friendship and relationship bars are at 100 and have been for two weeks IRL.
I have them go on dates, have meaningful conversations, joke around with each other, etc.
They're best friends, lovers, married. They're listed as deeply connected, smitten and closer from happy memories.

Yet, I cannot get them linked up as soulmates.

Did you ever find a solution? I'm experiencing the exact same issue with two of my sims.  

Update: 

This worked:

Pause and Ctrl+Shift+C

modifyrelationship <FirstCharNameFull> <OtherCharNameFull> -200 LTR_Friendship_Main
modifyrelationship <FirstCharNameFull> <OtherCharNameFull> -200 LTR_Romance_Main

Unpause and play for a few seconds - I had one tell a joke to the other then pause again

modifyrelationship <FirstCharNameFull> <OtherCharNameFull> 200 LTR_Friendship_Main
modifyrelationship <FirstCharNameFull> <OtherCharNameFull> 200 LTR_Romance_Main

(CM: Multiple posts merged. Check out this post for tips on how to edit and add more to a post.)