When adding several sheets to a Union in Tableau Prep, interacting with flow steps stalls and takes several minutes to load. Additionally, the flow ran in 1 second on 2019.4.1 but does not complete after one hour in both 2019.4.2 and 2020.1.1.
After upgrading to Tableau Prep 2019.4.2 flows stopped working correctly and performance regression was observed, but no error messages appeared, just spins running infinitely without actually processing the data. Downgrading to 2019.4.1 made flows work again.
While trying to run a .tfl flow as input node, the following error "System Error: Unable to run input node: Failure evaluating database:  hyper_execute_query:0 "db1003"."TableauTemp"."Sheet1$" does not exist." occurs. When running the same flow as .tflx, it works fine.
Flows with a large number of changes in a single clean step sometimes failed to complete.
Changing the color of an aggregate step had no effect.
Adding a pivot step sometimes resulted in a "Failure parsing AQL" error.
When connecting to TabPy or RServe with "require SSL" selected, Tableau Prep Builder closed unexpectedly with the error "Something went wrong and the application needs to restart".
Opening the Box connector showed the following prompt: "Do you want the application "java" to accept incoming network connections?"
Cloudera Hadoop sign in was disabled when only Cloudera Impala drivers were installed.
Clicking a "clean" step after clicking another step sometimes resulted in the error "System error: System error".
Tableau Prep Builder sometimes exported a 1 for an if-else calculation when a 0 was expected.