When the Reduce Recompilations that uses temporary tables feature is enabled by default on SQL Server 2019 by using Multiple Active Result Sets (MARS) connection, extra blocking may occur and it leads to performance issues. Additionally,the session ID of the blocker and the blockee is the same.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
This issue is fixed in the following cumulative update for SQL Server:
About cumulative updates for SQL Server:
Each new cumulative update for SQL Server contains all the hotfixes and all the security fixes that were included with the previous cumulative update. Check out the latest cumulative updates for SQL Server: