Last year I had a very similar problem, if not the exact same problem.
Overnight, all ootb SharePoint Workflows stopped working, with the error message:
Workflow XXX was canceled by System Account.
In our case, it turned out to be a security update,
SharePoint workflows stop working after you install .NET security updates for CVE-2018-8421
At the time ...
As per the Best Practices from MSFT:
To ensure optimal performance for farm operations, we recommend that you install SQL Server 2008 R2 with SP1 or SQL Server 2012 on a dedicated server that does not run other farm roles and does not host databases for other applications.
I could reproduce your issue on my SharePoint 2019 farm. The default value of the managed metadata column would not be displayed when new item.
Also, I find something interesting: I do not make the column mandatory, but give it a default value. When creating a new item, I leave the managed metadata column blank and click save. The managed metadata column of ...