As expected, our mistake! It was the “innocent“ call to a form that caused the problem.

The simplified schema of our system is:
1.Root EXE - purpose: determine the current version of the launcher and run it
2.Applications Launcher FXP - purpose: general setup, check user ID, customize the main menu.
3.Applications EXEs

In the launcher we had a DO FORM XXX, and that will load the class libraries in some, not all, WS memory. When the form was released, the class libraries were cleared, again, only on some WS. The CLEAR CLASS or CLEAR CLASSLIB didn’t help.

We put the Launcher into a project, included class libraries, compiled it to an EXE, and all is OK.

Thanks to all of you.