I never mentioned this bug because I thought the developers were aware of this at the time; only to realize it's still there. It can be reproduced consistently. Only if you are using the 'full screen gestures' for navigating instead of 'soft keys'.
You can make this bug happen(I think, it's consistent with my phone S20). It occurs when you have no apps open in 'recent tabs' and you got a notification from 'Secure Folder'; (I named it as 'Private Space') the notification from app(s) inside it.
To reproduce this bug: Be warn, I've only been able to get this bug to occur to my S20 since I have no other phones to work with; so the results may vary, Follow the steps below.
Step 1: Make sure the 'Secure Folder' or whatever you desired to name it (for me it's 'Private Space') is toggled off from the 'notification bar' ie... it should be grayed out; indicating it's toggled off.
Step 2: Close all apps and clear them out in the 'recent tab'. You may beed an external device to follow the other steps.
Step 3: Get a notification from an app that is inside your 'Secure Folder'. I've only get this to work with Snapchat since it's the only app that gives- notification frequently and quick. I assume that it works with every apps that are inside the 'Secure Folder'.
Step 4: Once the notification arrived, it should shows as a pop up and to your 'notification bar', click it.
Step 5: Exit out the 'Secure Folder' by swipping up at the bottom of your screen. It doesn't work when you're using 'soft keys' as your method for navigating throughout your phone. Use 'full screen gestures' instead.
Step 6: Go to the 'recen tab' and touch the bottom of your screen as if your intent was to swipe up to go to 'homescreen'. And you will now notice that the bug has occured.
The describing factors are:
The app which is from your 'Secure Folder' opens back up without your knowledge.
Even just touching the bottom of the screen, it opens back up.
An some other describing factor I have yet to discover...
I can't show you it in action because it does not let me screen record the content in 'Secure Folder'. And the content that I'm not willing to share are sensitive for public to see.