After saving project and opening it next day I got greeted with no subtools except the last one selected.
Also the “Tool” got instanced in zbrush (clicking one results as if you clicked both)
Resaving that the object as obj and reimporting it into the new project reduces size x200 times (so I assume missing information is in the initial file but does now load)
As you can see my project has number , but even previous version “16” seems to have the same issue
Hi EFROST,
the main reason for the file size discrepancy between the PRZ file based on your sculpting and the new file with the obj file could be mainly related on the UNDO-HISTORY function if you save your project.
http://docs.pixologic.com/user-guide/3d-modeling/undo-history/
Maybe (but I don’t believe it) this could be also the reason why you see only one subtool if you load your project file.
Could it be that your history slider is on the left position when you load your project file?
(I assume I’m totally wrong about this last item)
BTW: Please ensure that you have installed the latest ZBrush version.
CU and have a great day
Hi @eFROST!
There are many different factors that might make similar tool files based on the same geometry save at different sizes–subdivision levels, UVs, the state it’s in when it’s saved, etc. That in itself isn’t too odd, but the degree of the file size difference does raise an eyebrow. It might make sense if I had more context.
I don’t, however, understand what’s going on in the first screenshot you posted:
There is something not right there.
Please visit Pixologic Support, and Start a Conversation. It might save some time if you dropped by this page, followed the directions to create a Diagnostic Report for your version of ZBrush, and submitted that when you start your Conversation. It will save them asking you for it 
. They have the tools there to look into your issue in greater depth.
Take care! 
Hi , SPYNDEL
Here are more details how the file behaves
https://i.imgur.com/c7zbV0b.mp4
It has 186k and no Undo history , the tool is duplicated and acts as a instance when clicked for some reason. I have the latest 2021.1.1 version
Previous version which has multi million subtools (19 in total) weights about the same as file in question (about 606mb)
I can redo the work but just curious how this happened so I don’t have this issue if future )
I think after importing external obj I duplicated it and named it the same in both tools.
So I had 1st Tool with 20 subtool , and 2nd Tool with 1 subtool .But because the naming is the same ,subtool count got messed up maybe (so it doesn’t pick up that 1st Tool has multiple subtools )
Here’s the archived project itself if you want to see it
https://mega.nz/file/q0dBzSTY#FE0a-g5EpmHArtqWKY4nfkH3PH8aMKWaw5U8Mre_ZgU
Yup was able to confirm my suspicion
