Hi Winback,
Thank you for contacting Syncfusion support.
We have checked for the reported exception in SfTextBoxExt and we were not able to reproduce the reported exception from our side. We have prepared video for your reference and it can be downloaded from the below location.
Please check with the above video for the scenario we have checked and let us know if we have misunderstood your query. On further analysis, we suspect that “TabTip.exe” file is missing in your machine in the below location which may cause the exception in your side.
Location: C:\Program Files\Common Files\microsoft shared\ink
Can you please ensure whether the mentioned file is present in that location? If you are still facing the issue, can you please share the sample which replicates the issue? Also, share the Essential Studio version which you are currently using.
Regards,
Keerthana J