I have this problem also. I am using the Softaculous upgrade tool on a shared webhost. The Site was 1 12.x (12.6 IIRC) upgraded via Softaculous to V15.x, and has failed to upgrade to v18.
The Softaculous panel shows that it is v18 but the General configuration shows the following
Global site configuration, date formats, etc.
Database Version Problem
Your database requires an update to match the current Tiki version. Please proceed to the installer. Using Tiki with an incorrect database version usually provokes errors. If you have shell (SSH) access, you can also use the following, on the command line, from the root of your Tiki installation: php console.php database:update
Installer not locked
The installer allows a user to change or destroy the site’s database through the browser so it is very important to keep it locked.
You can re-run the installer (tiki-install.php), skip to the last step and select LOCK THE INSTALLER. Alternatively, you can simply add a lock file (file without any extension) in your db/ folder.
This is the current status from Softaculous
Apologies for the delay in reply.
It seems that this is the bug with the script itself. We have found a similar thread discussing over this issue and they shall fix this in the next version.
We request you to wait until then. Also this issue persist when an old Tiki that has been upgraded many times.
Let us know.