Unstallation of prerequisite with custom action

[AL1381]

Hello,

if have a install shield Setup.exe with chained msi packages and a separate setup.exe which is installed as prerequisite.
I need to uninstall the prerequisite during uninstallation process.

For that I created a custom action with return processing "Asynchron (ignore exit code) (I also tried synchron)

During install process of the setup.exe this custom action always interferes with the uninstallation process of the chained msi packages and fails to uninstall the prerequisite.
error 1618: “Another installation is already in progress. Complete that installation before proceeding with install.”

Is there any possibility to schedule the custom action properly?

Thanks for your help

[DLee65]

Unfortunately you cannot execute two MSI installs simultaneously.

Have you tried scheduling the uninstall as a deferred custom action? I haven't tried this personally, but that is the first idea that comes to mind.

[AL1381]

Yes, i've also tried the "Defered Execution". However the result was the same.