Okay, based on a comment by Amaris, I took out all my mods and put back in the Original IP world. I then did my normal:
Change resorts to community lots (except Hobarts, which I play in the test).
Change the fiesta plaza lot to delete stairs.
Evict all houseboat owners and relocate to land.
Delete the houseboats and their bases, leaving the ports. EXCEPT I leave the houseboats on the problem ports (Primavera & Premium) and change them to NVA (no visitors allowed). I also add a boat to Port Premium and make it and Port Playa (other problem ports) NVA.
When I go around to all the houses to check for problems, I then placed a vehicle for land and another for water on each lot. Some got two of each, if there was room.
It took me two whole days (but I don't just sit at my computer and do nothing else) to do this and I had lots already saved from earlier tweaking. (They just didn't have cars and boats.)
After playing for a few sim days, I did have what I thought would be a freeze. So, I quit my game and looked at the caches. One was well over 200,000. So I think that was the problem. I cleared the caches and when I reloaded my game, I didn't have any problems.
After playing about a week with Flo Hernandez who lives next to the Collins family, I noticed two kids stuck (one Ichtaca and one Collins kid) as the Collins parents were going inside. I had parked a car on their front area and the kids couldn't get on the lot from where they were. I'm not sure how that happened as they were using the car and getting along fine until then. So I might give them a motorcycle or some scooters OR park the car on the roof in my next rendition. :smile:
Any way, I discovered that it is possible for me to play IP without any mods. (I just prefer playing with Overwatch cleaning up for me.)