yeah, the edges around that surface don't look like the surfaces are joined properly to the surrounding surfaces.
First try this:
https://imgur.com/a/01TKEca Then save your scene and then export/update it to KS.
If that does not work, see if you have naked edges around that surface and close these.
To do this, select the surface and type this in the command line: _ShowEdges
If there are any, they will be highlighted in pink.
Type _JoinEdge in the command line and select the edges to join them.
If that does not work, you could export only the triangular surface and the surface around it, that should be fine to upload here. We won't need the complete model, just the parts that you are having problems with.
These are all quick fixes, your surfaces in that special area don't look very refined and if you want to avoid problems with your model in the future it would be best to rework that area and make the surface transitions smoother.
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I would have attached the image in the post, but somehow it did not work for me using the attach command here.