I've posted a ScriptError for this.
The problem is that the game constantly spawns service NPCs. I don't know which mod is causing it. I started a new game in a custom Sunset Valley, deleted all pre-existing sims, and added some of my own. As the time passed on the first day, lag started to set in. At first I thought it was just the game choosing jobs for the new sims, as this has happened before, but it kept getting worse. When I tried to save, it took 5 minutes, far too long for a town with all blank community lots and 9 residents. After checking though the mods, MasterController revealed that there were 1100 service sims, viewable only through that mod since they're "out of town". No matter how many times I delete them, they just come back. According to Register, I shouldn't have more than around 40, excluding animals.

Hi there,

From the Overwatch debugging report, it seems to be those pesky resort workers bounce, Overwatch is trying to clean them up but fails, if its still happening.

By any chance after the clean up, did you save, exit and reload and let ErrorTrap clean unused codes? Can you test this on an EA released world, maybe the original SV or a world that has Resorts (such as IP) and see if it bounces? It could be the Custom World itself.

Also don't run a Overwatch> Settings> Logging> on True (debugging purposes) to long when playing a live game, it could be a source of the lag where its coming from by logging every single action OW does.

Grts.

I'll try the original Sunset Valley and Isla Paradiso without ErrorTrap and then try the custom world with it.

Maybe keep ET in, it might be useful on catching any errors that are useful to read and they may without it remain hidden otherwise.

I let Sunset Valley run for 3 sim days. Checking MasterControl, the pool stayed around 70, jumping a little on day 2 for the festival. I then loaded the custom world and tried to invite the sims over. I made my sims know them all by way of the mailbox. Only a few had thumbnails. The first was a mailman, and the next 5 were teens. The game then crashed before the last two sims came over.
I haven't run Isla Paradiso yet, since it's always too slow for me.

I just added ErrorTrap and ran the world. Not only did the service pool still increase, but also the game started throwing error messages non-stop. I shut the game down around the 400th one without saving. I now have 11 new ScriptError files. Should I upload those as well?

Yes please, the same way as you did the other. If you have multiples, just add them into 1 zip file.

Also, can you try one game, with just NRaas mods in your Mods\Packages\ folder. Move all other mods in a temporary folder on your desktop, just to see how it runs with NRaas only, don't forget to clear your Cache (especially the ScriptCache.package in your Sims 3 userdirectory).