The dialog is the Booking picker, and it opens only when a Book button has no location attached: no Booking center ID on the block or section, and no Default center ID under Theme settings → Booking.
Fix it in one place
Open Theme settings → Booking and fill in Default center ID with your main center's ID. Every button without a center of its own now books that center, and the dialog no longer opens for them.
Or give the section its own center
On a section that belongs to one location (a location page's menu, a locations grid card, a plan on a location-only page), fill in Booking center ID. That section's buttons book that center whatever the default is.
When you want the dialog
For a multi-location group, the dialog on the home page hero is a feature, not a bug: the guest picks a location before Zenoti asks them to. Leave Default center ID blank on purpose and keep the picker's location blocks up to date. See Book buttons and the location picker.