Romance bar decays within seconds

The romance bar is decaying back down to zero within a matter of seconds after getting it up. This didn't occur until I downloaded the Lovestruck Expansion.

 I see that there is an archived bug report from 10 months ago that says it has been resolved, but it is happening to me and it is game-breaking. I can't make any new romantic relationships with any sims, which is kind of the whole point of the Lovestruck expansion.