Hi Rachael,
Sorry for the delay in getting back to you.
Herewith i have attached a sample, in which GridGrouping control is placed inside a multipage which is embedded within a callback panel.
http://www.syncfusion.com/Support/user/uploads/Grid_13a6b0db.zipPlease try running the sample and let us know if your facing the same issue as in the attached sample.
If so, this issue has been resolved in our latest version which is ready for testing.
Please let us know if you have any other queries.
Thanks for your patience.
Regards,
Valli