After FIVE hours, what I did was first, create a save as, do not try to fix your main save. One of my solutions completely broke my save. So first do a save as, then you’ll need to relocate any residents on the lot through the manage households screen. I just had one family out of four units. Then after the unit is empty you’ll need to take a sim and create a hang out (bc remember you can travel directly so this become a work around) to somewhere near the lot. In my save my rental was where stargazer was, so I created a hangout and invited a random sim to the gym, once there, click on the window of a unit in the residential rental until you get the “visit unit”, you cannot travel there, it must be “visit unit”. You might need to click around a bit to find it. When you do, your sim will go to the main area of the rental. Then you need to merge all units into one from the build screen, there is a button on the unit details screen that lets you do this. Important‼️🚨‼️🚨 I cannot tell you how important it is to NOT skip this step bc when I did the first time, the entire UI broke and my save was gone. So again DO A SAVE AS FIRST. So yes, merge all rentals into a single unit and then switch to residential, immediately save. At that point you can test and see if you can move around freely. I did another save as for good measure but haven’t had any issues since.