All bezier curves blocked after document is reloaded

1) Create new Project/File
2) Add timeline to file
3) Add a few simple keyframes using the global record button
4) Open graphical curve editor
5) Add handles to keyframes (spline toolbutton)
6) Adjust handles/keyframes
7) Close curve editor
8) Change/close file
9) Open the original file again
10) Open curve editor

expected: curve can be still edited
result: it is not possible to edit the curve (purple)