Hi Charlotte,
Thanks for contacting Syncfusion support.
We have checked the reported issue and made sample based on the provided code snippet. While checking the issue in the sample, we observed that on typing above 30 characters, value becomes null when focused out. Please confirm whether you report the same issue. If this is not an issue reported in your end, then kindly provide replication steps to reproduce the issue that will help us to validate the issue further and provide you a better solution from our end. Please find the sample in the below link.
Screenshot:
Regards,
Jeyanth.