Then it’s at least not an AFPS issue as this command always uses HFS+ (more compatible to older macOS versions and less buggy).
Still working since yesterday!
Thanks to all willing helpers!
Hi, I experience the same problem. Encrypted database (created under Mojave) are going to automatically unmounted after <1h. Will give it a try to create new a encrypted database under Catalina and transfer the data afterwards, as here reported.
On one of my Macs with Catalina the issue occurs although i have created a new encrypted db…
Just gave it a try, even a newly created encrypted DB under Catalina is being unmounted automatically. This time after 5min without use.
Actually it corrupts my DB, since files are being imported while the DB is being unmounted. Afterwards files are either not located in the DB (but can be found as orphaned files) or are blank pages!
Anyone a hint how to fix that?
Right now I return to an unencrypted DB, since my document management is to important to use a unreliable technology!
Hi to all,
I also have this issue. Created the encrypted Databases in DEVONthink and Mojave. All workes fine.
Since I upgraded to Catalina I have this issue.
I reinstalled DEVONthink, I also created new DB under Catalina - nothing solved the issue.
Think I also need to go back to unencrypted DB until the issue is fixed.
How do you move back to unencrypted DB? What is the easiest way without loosing anything?
THX for help.
Select an item in your database and show in Finder. Go to the upper level and you will see the database (unencrypted) inside the encrypted disk image. You can copy it out of the disk image and use it as an unencrypted database.
After copying please close the encrypted database. Then you can open the copied one.
got it - do I need to close the DB in DEVONthink before copying?
No, because closing the database will unmount the encrypted volume. Then you can’t copy 
true - thx!
Right now I return to an unencrypted DB, since my document management is to important to use a unreliable technology!
There is nothing showing the technology is unreliable. This is only occurring in macOS Catalina from the reports here.
To you and to @Nik: Where are the .dtSparse files located - the file path on the machine?
Hi Bluefrog -
the Files are located on my local drive (SSD) in a seperate folder…see screenshot…
Thx for support
…to add…since I have this machine…and was working before…
since I have this machine…and was working before…
Was working before in Catalina… or Mojave?
Was working in Mojave - since Catalina I have the issue…
Yep… as I suspected.
Ugh… but thanks for the corroboration. 
@BLUEFROG, I cannot determine whether the automated unmount happened under Mojave or since Catalina since I just recently switched to encrypted DBs but have noticed the effect just recently.
The DBs are located locally in a regular folder.
We are investigating this and trying to reproduce the issue. Thanks for your patience and understanding.
I have created the encrypted sparsebundle image (APFS) with the disk utility, copied the database in it and changed the suffix to dtSparse. Since then (12 hours) it is not ejected.
If this is accurate, I hope this doesn’t mean Catalina will be unfriendly to HFS volumes. 