Hello Kaneva! This definitely sounds like a heavy model issue. Or, an under-powered hardware issue?
You have nailed it with the troubleshooting process. That’s exactly what I would have done. The furniture is your culprit. You should add in 2d graphics/3d objects for those too.
ConDoc is rock solid in what it is doing. but if you ask it to shovel 100mb of model it will take a moment, especially if your hardware is not up to spec. Which I don’t know if it is or isnt’t! I hope this helps!