Hi Rob,
Greetings from Syncfusion support.
We have validated the issue with the provided details .But unfortunately we couldn’t able to reproduce it in our end with latest version(19.3.44). Kindly refer the below snapshot and sample for your reference.
[SnapShot]
If you still reproduce the issue kindly provide the following details to proceed further in our end.
1.If you rendered the combobox inside any other components like dialogue ,tab etc..
2.Simple sample or modify the provided sample which reproduces the issue.
3.If any specific replication procedure to reproduce the issue.
4.If you have used any custom styles to modify the UI appearance of the combo box component or overridden the existing styles.
The above details will help us to analyze further and provide you the better solution.
Thanks,
Deepak R.