Hi Jozef, I've attached a fixed version here with that little tiny extra slivers removed. Please give this one a try.

- Michael

With one simple cut operation (cutting the protruding cylinders) the stl export is OK.
J.

Hi Michael
thank you...

I did not refresh the page, I achieved the same result.
Jozef

HI I use Microsoft 3d BUILDER to repiair STL or OBJs before printing its free its built on NETFABB engine which AUTODESK bought its super tough in doing repairs I use frequently when going from MOI to ZBRUSH or back. Even in complex ZBRUSH models with inner non manifold surfaces it always corrects the STL to be watertight for printing. I also do resin based jewellery prints and pass it through 3d builder to correct any problems before printing. Hope that helps.

https://www.microsoft.com/en-us/p/3d-builder/9wzdncrfj3t6

You have also the MeshMixer who has a function Analyse / Repear... for STL files

https://www.meshmixer.com