It's been a long time I'm struggling with this problem and I cannot wait more for this to be fixed as I'm always working on multiple projects in the same time.
For example, I'm currently working on ten different projects that I need to be open in the same time in Premiere Pro, as I'm constantly switching from one sequence to another through all those projects (This helps me to copy/paste effects and so on).
I don't know why it's doing this but when I have all those projects open with their sequences and that I decide to switch from one of my custom workspace into another custom one: the software is randomly closing projects and sequences, and it only keeps some of them open into project/sequence panels.
That's really annoying, this means I always have to open them by myself one after another every time I need to change my workspace...
Being able to change from one workspace to another is a powerful tool but in those cases, it destroys my all workflow.
If that doesn't work, try resetting the Workspaces: Reset a workspace Reset the current workspace to return to its original, saved layout of panels. 1. Do one of the following: • Click the Workspace menu icon and select Reset to Saved Layout. • Choose Window > Workspace > Reset to Saved Layout. from here: https://helpx.adobe.com/premiere-pro/using/workspaces.html
If that doesn't work, try Preferences > Audio Hardware and set Input to None.
in windows OS kernals are used to open more than one program at a time... basically the computer is saying, " oh, I have to open another program, so I have to pretend I am more than one computer ( kernal ? ).
This works pretty good for simple stuff but with editing the resources needed get very demanding on your computer memory, resources, etc. I think.
If you are openening 10 projects at a time to edit ten movies at the same time I am astounded at your brilliance to be a creative editor !
Maybe keep it down to only editing 2 movies at once and see how that goes ??