I have a docx template file that contains both MERGEFIELD and CheckBox.
Using version 2021.1.118 of Telerik.Windows.Documents.Flow I perform MailMerge on that document.
After mailmerge the Checkbox control in the output document looses its style when being manually triggered. Manually triggering checkbox in original template does not change original style.
It's expected, that after mailmerge the Checkbox behaves as before mailmerge.
The complete demo is here: