June 2020
I am having this issue. Here are my save files: https://1drv.ms/u/s!Agz9k3UFAizZiC5pJGy2lBa5Css1?e=Vbbly1
I also wanted to add that the "Stay the Night" option is available on community lots. Nothing happens when selected.
Here is an image showing the issue:
June 2020
I am seeing this now on PS4. My married Sims can invite one another to stay the night.
December 2020
For the record, it's still happening. As someone else said, it's not game breaking but it's a weird thing for couples to say to one another.
December 2020
I don't think this is a bug. It's been happening since the base game. They just forgot to remove the interaction between couples living together so it pops up even if their living together.