When you are fighting to stay below that magical 99.99/100 memory limit, have a look in your “World Settings” if you don’t see it docked bottom right go to WINDOW > World Settings…,
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Check/Tick “Enable streaming” is on.
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Temporarily enable “Preview Grids”.
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Expand the “Grids” section.
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Look at the size of your cells (I have mine set at 6400 but you might like something bigger) the smaller the cells the more granular will be the memory calculation.
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Look at the “Loading Range” ie; That’s how much is kept in memory at any one time and what the player can see (My loading range is set to 10000 - Ten Thousand)
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Make certain that your biggest assets & devices are spread out to less memory heavy areas, or are in different cells. I did an experiment where I put all the vehicle devices & 6 BIG Prefabs in the centre of a brand new landscape, it was about 150/100 - then I spread them to individual cells AND checked nothing heavy was within the same “Loading Range” and it went down to around 75/100.
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With the recent update to 25.11, Look in the “Message Log > Memory Test Results” (After uploading to a Private Version & performing a Memory Test) There is a new line at the top with a link to the “Highest Memory Location” on your island.
Hope that helps Guys!! 
Carl