This has been happening to me too. I'm at 4999/5000 with my husband and I can only take him on a date in Vegas, and even after that date, there is no advancement. I'm stuck at 4999/5000.
I can't get any further in my relationship with my husband either. I'm at 4999/5000 and I can only date him in Vegas but after I do that nothing happens! No advancement, NOTHING!!! So annoyed!!!