I solved the problem.

The reason for the problem was that I set the autosize for some of the
ib_text to true. If you set it to true, the grid becomes crazy.

What drove me crazy was, that I could not explain myself, why it works
on other forms, but this was because there I had no ib_text with
autosize true.
On the new form I had a ib_text with autosize true and it worked
sometimes. I found out, that it works, when the displayed string from
the datasource is shorter then the name of the component, so that it
does not have to expand the component. For example if you name the
ib_text myrealylongib_textcomponentname you will not get a problem
when the data displayed is for example "short data". If you name your
ib_text ib_text1 and the data is 'a longer data to display', then the
grids get out of control.

For me it means: autosize should allways be set to false for ib_text.

Kind regards
Helmut