Previously Saved Builds Missing Across Worlds

I have recently discovered that significant (days worth) work on previously saved builds have disappeared from my primary save file. This is not progress from a single play session that merely failed to save, but rather, multiple builds that had been worked on, saved, returned to, worked on, saved, etc. I primarily use The Sims for building, rather than live mode, and I have done extensive recovery work to determine what could have gone wrong. Here is a timeline of what I have discovered:

July 23rd - most likely my first time playing the game since the July 21st update. This is also most likely the day I started building a substantially large build in Windenburg that I will name the four-townhome lot. This lot was a basic residential lot.

July 24th - I have evidence that I was actively working on the four-townhome lot. While building, I was experiencing significant crashes. Over time, I determined these crashes were happening due to attempting to place walls and/or stairs in specific areas. Due to this, I saved an unfinished version of this lot to my library while troubleshooting. This copy contains a mostly finished exterior, an empty interior, and one specific staircase that I was having difficulty placing.  

July 26th - I have documentation that I was still working on the interior of the four-townhome lot. This build eventually was completed in its' entirety, taking place over a series of days and sessions, saved after each session and returned to with no issues.

Aug 3rd - I began working on a new residential build that took place on the Moppy Manor lot in Ravenwood. Around this time frame, I also began another residential build on the Old Salt House lot in San Myshuno.

Aug 13th - I have a weekly recovery version of my primary save from this date. By this recovery points, the missing build problem had already occurred. In this recovery file, and in my current save:

• The four-townhome lot has been reverted back to it's early construction state, matching the version I currently have in my library. The interior is empty and the one staircase is missing.
• In Ravenwood, Moppy Manor is still bulldozed, but my build is completely gone.
• In San Myshuno, Old Salt House is bulldozed but my build is gone. 

Separately, there are two lots in Coppertown that I worked on more recently that are also gone; however, they have reverted back to their original EA build.

This does not seem to be a straightforward rollback to an older version of the save. If it was, the original EA builds in San Myshuno and Ravenwood would still exist. Instead, they remain bulldozed while later build/buy data has disappeared. I have three other save files and I have checked them all to ensure I did not simply place these builds in another save. All the original EA builds remain in those saves.

I have checked multiple recovery versions. The July 23rd monthly recovery predates this work, while the August 13th weekly recovery already exhibits the data loss. I do not have an automatic recovery point between those dates.

I have preserved a backup of the affected save and its recovery files. I checked available in-game recovery versions, other manual save slots, Windows Previous Versions, and attempted deleted-file recovery with Windows File Recovery. There is no intact version from the period when these builds existed. My affected primary save is Slot_00000002 and I can provide that save, and it's recovery files if it would be useful.

Another potentially  relevant observation: during this period of time, I recall experiencing unusual build mode behavior in which the colored rental-unit boundary lines would unexpectedly appear despite being in residential mode. Changing the lot type to something different, and then back to residential, seemingly resolved this issue. This happened on numerous builds at random points.