Sorting issue in a datagrid

[André Bisseret]

Bonjour,

I have a data grid (table) with 3 columns, forty lines (currently).

When clicking on the header of column 1 or column 3 all is working well (the lines are sorted as expected)
But, when clicking on the header of column 2, only the 8 first lines remain (correctly sorted). All the other lines disappear!
Now, if I sort column 1 and then I sort again column 2, only 3 lines are remaining in the datagrid!

For a couple of hours I tried to find what was wrong in my setting ; changed the header of column 2, built a brand new data grid, …
 but with no avail!
I am lost

First time I get such an issue in a data grid.
 
any idea on what could be happening would be very much appreciated

 Best regards

André