Woohoo option not on object for certain sim

My sim met this new sim that the game generated, and they flirted and first kissed and brought the romance bar all the way up.

I can now choose 'woohoo' from the romance menu by clicking on the sim, and they go woohoo in the bed, no problem there.

However, when I click on the bed and choose woohoo, the new sim doesn't appear in the list of available sims to choose from. Other sims that I've romanced appear in the list, just not the new one.

So I can woohoo with that sim from the sim's romance menu, but not from the object menu. And this only happens with that specific sim.

Any ideas ?

Thanks ahead