STL export cant sum the mesh

I was exporting an object made of multiple objects to STL, and now the parts that touch are subtracted (like boolean difference)… someone knows why is this happening? I used this function a lot of times to 3d printing and objects melted in one before (before blender 3.1 I guess).

Examples:

Here you can see my last model the lady tiefling, 154 objects, impossible to bool sum one by one… figure 1.

Them you can see the results of stl export on blender 3.4 in CURA slicer to 3d print (figure 2) and the results of stl export in blender 3.0 (figure 3).

To show better the sum effect I take this 3 extra images in chitubox, another model (figure 4), STL export on blender 3.0 on chitubox (figure 5) and the same but blender 3.4 (figure 6).