When you do some crafting and enter the sandbox, it duplicates the item you were crafting, fills your inventory and splashes some items on the ground.

Here is my save: https://drive.google.com/file/d/1OD2aCMy-X_DM8XARsFCar_99vI0CzLgU/view?usp=sharing

Load the save, immediately enter the sandbox and wait until the blue assemblers finish to be crafted.

The initial blue assemblers crafting count was 37. The result: https://imgur.com/a/i3lzmhb

This definitely seems like a bug within Factorio, but it's complicated enough that I can't quickly make a small enough reproducible example. For now, I've swapped the newer "enter as remote view" behavior into a setting and defaulted it back to the old approach of "enter as a god," since this does not happen. Remote View still works, of course.

It fixes the bug. Thanks !