Hi! I need to ask some basic questions to drill this down.
1. Is the button present in the main Timeline only from frame 217 onwards, or is it actually present from frame 1, but made visible with scripting in 217?
2. Are you sure it really is a button symbol you're using? It must be set as such both in the Library AND in the property panel dropdown. You can turn one symbol type into an instance of a different type this way you know, and sometimes unintentionally. A Button type symbol turned into a Graphic type symbol would play to the last frame and stop there, which indeed is the click zone of the original Button type symbol.
3. Does the button work as expected when you click on it?
Her lips said "no!" but her eyes said "read my lips".