Hi Gianandrea,
Thanks for using Syncfusion products. We identified a small recycling issue with the template renderer, this is corrected in a simple sample itself,
http://www.syncfusion.com/uploads/redirect.aspx?&team=support&file=sample1634466832.zipIt loads up a 1000 rows with buttons as Templated cells. Please use the modified GridDataBoundCellRenderer present in the sample, and let us know your results. If you are still seeing the same exception, then we would want a sample that replicates it. You can create a Direct-Trac incident for quick follow up on bugs.
Thanks,
Fahad