Guests won't sit down at my wedding ceremony

The same thing happens in my weddings. I used the premade room for the first few weddings I had and everyone sat down when the ceremony started but now if I place an arch and chairs myself everyone just stands around and will only sit on the chairs after the ceremony when they want to eat or talk. At first I thought I placed the chairs too close or too far from the arch, but after playing around with chair placements and having multiple demo weddings ruined because of standing sims I realised it must be a glitch in the game. I only really noticed this happening when I use my own (or others from the gallery) wedding setup, so for the next wedding I'll use the default wedding room and see if that still works.

I also wonder if it could be a chair issue? Perhaps they'll only sit down for a wedding if there's bench just like the one in the wedding room? I also tried using the chaises that come with Luxury Party Stuff and that didn't work either - they all stood around them but still had no problem sitting on them when they wanted to eat. I also hate that they go to sit by the arch to eat instead of by the dining tables that would be conveniently placed near the buffet table.