Tablegrid scrolling problem

Good Evening Dmitry,
This may be a small bug or the way my script works.
1.  For each row in my tablegrid, I make an sqlexecute call to retrieve some text to display in a memo field.
2.  When I click on the next row down, the text in the memo field changes.
3.  This works until you reach the last VISIBLE row on the grid (the row BEFORE the grid starts scrolling down).
4.  From this row onwards, the text in the memo field no longer changes.
5.  To work around this, you need to click 'scroll-down' to move the whole grid down 1 row and then click on the row again.
6.  I have changed the design of the form, giving the tablegrid less and more rows and the problem always repeats wherever the last VISIBLE row occurs.
It seems as if MVD cannot determine the tablegrid.dbItemId after the last VISIBLE row in the tablegrid. 
I have attached my project so you can see the problem.  I am currently using Version 1.50.
Thanks,
Derek.