Running Neoload 4.2.2.
There was a SQL cluster change made on 2-26.
Problem started then.
When I run the SQL query from SQL Server Management Studio it still works 100% of time.
When I "test" the same query from Neoload SQL variable: it works - it does not work - it works - it does not work... It doesn't matter what SQL variable is tested the pattern is the same. Stack trace is attached.
According to the description of your issue and the stacktrace, a timeout seems to be the root cause of your issue.
You said that it works from SQL Server Management Studio, is it from the same machine?
How did you setup the SQL variable connection? Is it with the IP or hostname of the SQL server?
If you try a traceroute of your SQL server do you get high response time?