Tuplets that contain notes that produce beams, such as eighth notes, are beamed together. However, special beam grouping rules apply to tuplets within beams that also contain non-tuplet notes.
The default setting for a tuplet in a beamed group with secondary beams is to split the secondary beam and to show the tuplet with a bracket. The primary beam is not split. If necessary, you can hide/show tuplet brackets individually.
The default setting for a tuplet in a beamed group with only a primary beam is to separate the tuplet entirely. However, you can change this setting on the Beam Grouping page in Notation Options.