Hi Adam,

I am measuring your wall thicknesses at 0.02 mm. That is impossible to 3D print with current machines.
If you are using an FDM machine, take your nozzle size+0.05 mm for the minimum wall thickness to ensure good slicing.
Set the line thickness in your slicer also to somewhere around this value - sometimes setting it a bit lower makes for better prints.

Also use boolean-union functions to combine multiple meshes may make for better slicing. Send me a PM if you want me to help you further with preparing STL files.