Hi Mani,
Thank you for your interest in Syncfusion products.
I am afraid that I was not able to reproduce the issue that you mentioned here. I have created a sample with 1000 rows and test this issue but the issue not reproduced.
Please refer the sample in the below link:
http://websamples.syncfusion.com/samples/Grid.Windows/F72635/main.htmPlease have a look at the above sample and if still the issue exists, could you please try reproducing it in the above sample or send us the reproducing steps so that we could sort out the cause of the issue and provide you a solution?
Regards,
G.Yavana