[TYPO3] dynaflex: pressing save twice to get new number of sheets

[Johannes Konert]

Hi members and Thomas respectively, who created a powerful extension,
I'm having a small fight with dynaflex:
The manual says: "If you use a fieldvalue as source for one or more 
modifications, the changes take effect after second save and not after 
the first click on “save”. To avoid this, you can use another hook in 
the tceforms class. This hook is called “getMainFields_preProcess”."

So I use both hooks as well as the dynaflex_tut does, but neither mine 
nor the dynaflex_tut does now process correctly on ~first~ save.
With the tutorial I put "number 4", pressing save, nice: getting 4 sheets,
I put number 2 (so lower than before!), press save, nothing happens 
(still 4 sheets)!, press save again, now the sheets are reduced to 2.

Has anyone had this problem before?
I doubt it is related to any TYPO3-configuration in general because it 
happens on two different servers with 2 TYPO3 v4 Installations.

Help appreciated :)
Cheers,
Johannes