Impossibility to print with three holes

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Hi there,

I am usually designing with blender and then exporting in .stl

I modeled a quite simple object containing three holes. Once imported in Cura, the solid view looks perfect (the three holes are visible) but when I look at it with the layer view, two of the holes vanish and the object contains only one. I tried to launch the printer anyway but unfortunately, the result is identical to the layer view (without two of the holes). I suspect an improper conversion into .stl (blender's fault) or a misinterpretation of the file (cura's fault). Have you ever experienced that? Does anyone have a trick to solve this?

Thanks,

Remi