High School Years Auditorium enters Build Mode, despawning items during Prom

Would you be willing to share your backup save with me (before it happens)

If so, upload it somewhere like dropbox, googledrive or OneDrive and PM me the link.

I did not change anything about the auditorium. When it happened the first time, I exited back to main menu to reload the previous save. When my sim showed up at Prom I saved it. Every time I reloaded the save with my sim already at the school almost immediately, I get a pop-up on screen saying "BUILDING LOT" and when the lot finishes loading the items are missing as shown in the image above. 

Did you change anything about the auditorium or is this the original one in every way ?

Gave this a short test on an existing save and it worked fine for me. No despawning.

Does it happen every time for you ?

Even with the mods/CC setting turned off this bug occurs.

The only CC I had in my game was a modified version of the Flower Beard from the Enchanted by Nature Expansion Pack without the flowers.

The recap is accurate. My teen sim is at prom and almost immediately the objects despawn before I can complete any tasks.

Hi DynamicBookworm​ 

To be sure, you never had any mods/cc or did you remove them ?

Also to recap, this is what happened: 

1. Prom triggered and your Sim went to prom
2. All spawned correctly as it should
3. After a while stuff started despawning although the event wasn't over