Hi Brian,
Thank you for your interest in Syncfusion products.
I am afraid that I am unable to reproduce the issue in GridGroupingControl when the numeric up down cell is used.
We have created a simple sample to test the issue with GridGroupingControl as below and followed the mentioned steps in this sample.
http://files.syncfusion.com/support/samples/Grid.Windows/7.3.0.20/Forums/GGCTest.zipPlease have a look at the above sample and if the issue still 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,
Lingaraj S.