I've been having an issue with this as well, but it seems to be specific to a certain couple. If I try to have them WooHoo in their bed (both by selecting the WooHoo option from one of the Sims and from the bed itself), they try to go to a different bed. They shoo out anyone who is there, and then don't always WooHoo. I rearranged the room so nothing is near the bed, I reset the bed, and I replaced it. No change. I also had it happen at a different location. I went to the bar and had added two of the pre-made bedrooms. Each time I tried to WooHoo, they would go to the other room but not actually WooHoo. They just kept going back and forth, and ultimately ended up having a conversation through a wall. They WooHoo in the observatory no problem.
I'm wondering if there are some pathing issues, because I also have Sims go to weird places (the most common one is my Sims taking their dishes to an upstairs bathroom instead of the kitchen).