In this particular case, as the original mesh is a mess with open edges everywhere, I would just rebuild the object in NURBS, it’s pretty simple and will be faster.
I traced the profile of one of the spokes, did a Revolve of 180° of the trace and capped it to make a solid. Then I made 2 new circles and extruded them to form the inner ring. PolarArray’ed the spoke around the center 40x. Finally BooleanUnion’ed everything into one solid object, ready to export as STL. Here the exported .stl is perfect.
Bracelet 5 halved-rebuilt.zip (3.0 MB)