@kittypride Ok, downloaded the lot and have taken a look at it in build and live modes. Had a sim buy it and go there in live mode. There are a few things I would have done differently but as far as I can tell, the lot works, at least as far as I can tell.
I did not get the unit labeled like you did in your first pic. No unit is labeled A, B & C. All the units are labeled 1 - 5 Hounds Head. Units 4 and 5 were just 1 tile squares which I assume are from when you were troubleshooting. Three of the buildings were assigned to unit 1 with single buildings being assigned to units 2 and 3. When my sim landed on the lot after buying it, you can see what you are supposed to see - 1 Hound's Head and Shared spaces are furnished, the rest are hidden including the little 1 tile basement with the nectar rack and the shared basement. Then I found tenants for units 2-5 and moved in my sim as landlord into unit 1. Next, I traveled to units 2-5 and checked those. I didn't find any obvious problems with any of the units. As far as I can tell, everything works as it should. The lot display from the map was as it should be as well. The only odd thing I found was the icon for unit 1 didn't show up when in map view. That, I am assuming, is because there are 3 buildings assigned to unit one and the game didn't know where to display it. Clicking on any of those 3 building would take to the lot though. I see a bit of the same in my residential rental build where I added a basement storage room for each of the 6 apartments in the building that is separated from the apartments and you get to them through a shared space.
Next, I evicted all the tenants, sold the lot and went back in build and deleted the 1 tile units and created new units for 2 of the buildings assigned to unit 1. After doing that, the icon for that unit displayed properly in map view. Then I bought the lot again, found tenants for all the units, moved the owner into unit 1 and checked the lot over again, traveling from unit to unit. I found no problems, and everything acted as it should. I also got no errors while I was testing.
So, in a nutshell, I found nothing wrong with the lot. Everything worked just like it does in my own residential rental build. There is a difference though, as I play and tested the lot on PC where you built it and play on a PS4. The lot is a 64x64 and according to a friend who played on PS4 and now PS5, the PS4 tended to struggle a bit with the large lots. Maybe that is part of the cause for some of your issues with the lot but tbh, I don't know that for sure as I haven't played on any of the consoles.
One thing you can try though that I found will help with some lots that are throwing errors and have other issues at times. You can try saving the lot to your Library, then bulldoze the lot and replace it with the copy from the Library. From what you've said, you've already tried the other things I usually recommend for troubleshooting a lot, so I don't really have any other advice for you.
Hope this helps.