Hi Sam,
My sincere apologies for the inconvenience caused.This is an already known issue and it has been fixed in later versions.In the later releases, TreeViewAdv control has a rich set of features, lots of bugfixes and other improvements.We strongly recommend you to switch to v.4.2 and you could upgrade to the same from the download instructions given below :
4.2V DownloadLink
Let me know if you need further assistance. Thanks for your interest in Syncfusion products.
Regards,
Deepa