Applescript, XCode: Launching application 2 from application 1 crashes application 1

I have the following scenario:

In application 1 (XCode Applescript app), I have a button which launches application 2 (a similar application).

When testing the build out of XCode, this works. The development system is macOS 10.13.6, XCode 10.1).

When trying it out on the test system (macOS 10.14.6, virtual under VMWare), or on my client’s system (macOS 10.15 and 11.2), application 2 launches correctly, but application 1 crashes (it does not terminate, as there is some housecleaning going on when terminating).

I have tried the following commands (we are in an Applescript environment):

• tell application "" to run
• do shell script "open -a"
• set runopti to "osascript /Applications/ > /dev/null 2>&1  &" 
  do shell script runopti
• set runopti to "osascript /Users/Shared/xxx/startapp2.scpt > /dev/null 2>&1 &"
  do shell script runopti

The first and second lines also with the absolute path to

I am sure that I miss something obvious, but what? Or do I have to give special permissions somewhere?

Any help and tip are highly appreciated.