I prepared a little demo based on your demo Biolife ClientDataSet. I added column with TButton as Custom Control in last column (Column 8). I click the button and then move the vertical scroll bar briskly by grabbing it with the mouse. I repeat this several times and as a result, all or part of the TButton disappears. Can you look at this problem, please. I'm working with latest version 6.3.1.3 on Delphi 11.3 VCL.