Now i have found out what caused my problems:
Suppose there are 2 packages: package1 and package2. Proc p1 is defined in package1-procs.tcl and proc p2 is defined in package2-procs.tcl. Proc p2 is calling p1 at some point.
The problem is this:
Every package-proc.tcl file is reloaded again after some time. Sometimes package1 is loaded first, sometimes package2. If package2 is loaded first it does not know Proc p1 as package1 has not been loaded.
How can i be sure that package1 is sourced before package2 ? Would it help to define a dependency in the package manager ?