I found a wall out of place in the ICMP in front of the Main Ingredient. It looks like the store front is in the walkway, but I can walk through it. I selected the Refscope spell and it returned:
Ref:000FD7BA Temp Oblivion.esm
Stat:0003D015 Temp Oblivion.esm
If this a mod conflict, why would it return an object in the Oblivion.esm?

Because mods can move vanilla-placed objects. Looks like you need to do this the old fashioned way, and start disabling mods until the problem goes away so that you can find which ESP is the cause.

Or load up all your mods in TES4EDIT and see which ones edit those two references.

Does it look like the picture in this thread? http://www.gamesas.com/index.php?/topic/1115941-graphic-errors-in-towns/

Tried TES4Edit, but the objects it referenced didn't make sense. After going back to the scene, I didn't find any problem.
Also tried removing the Minimap mod as suggested in another thread, but that has no effect. I'm so glad it wasn't the Minimap mod, don't know if I could go without that. Also ran TES4LODGen again as suggested. Problem seems to have disappeared, for now.
Thanks for all your suggestions!

Looks like one of those double-door issues we see with Better Cities every once in a while. Those floating doors disappear once the cells are purged or something (Ismelda explained but it went over my head then).

Yeah, I'm just glad it's gone.