It should be wrapping, so if the cursor is at the end, it should start from the beginning. That's the behavior I'm seeing with our demo projects.
If not, it could be something about your usage, but a simple solution is to position the cursor at the start when you call RapidSpellDialog.Check()
If you'd like me to look further, please provide code showing what you're doing.
Jim
-your feedback is helpful to other users, thank you!