Jenkins: Windows build re-started elevated breaks with "Build already in progress"

Question

In Jenkins, I have in a function that has

powershell '& "C:\\Program Files\\VisBuildPro9\\VisBuildCmd.exe" /logfile myLogFile /nologo myBuildFile.bld'

This used to work fine until factors beyond my control caused this script to have to restart elevated. Jenkins output:

3/10/2022 9:38:06 AM: Starting Build: myBuildFile.bld
3/10/2022 9:38:06 AM: Building project step 'myBuildFile.bld' was restarted elevated'...
Pausing 3 seconds...

Error building application: Build already in progress.

Now if I run myBuildFile.bld in the Windows system that is the Jenkins agent, Visual Build Professional does something similar, spawning a second (elevated) VBP which runs the build without complaining that a build is already in progress.

How can I get past the "Build already in progress" block in my Jenkins script?