SOR filter not always working

[nikoue]

Hello. I scanned an airport using a RIEGL VZ-600i in kinematic mode. These scans contain significant noise at the bottom of the scanned area. CloudCompare’s SOR filter does an excellent job of removing these points.
However, I have a problem. I tiled the whole cloud into almost identical parts (with nearly the same number of points). Although the procedure is slow, I was able to clean many of the tiles successfully. But for some tiles, the SOR filter starts processing and then never finishes. After a while, it becomes obvious that CloudCompare has stopped using system resources and remains in a non-responsive state.
I have also run the procedure from the command line with the same results. I even tried heavily simplifying the problematic tiles using the octree method, but they still fail to process.
Can anyone think of what the problem might be?

[daniel]

This generally happen when you have many points at the same location. Can you try using the 'Tools > Other > Remove duplicate points' on these clouds first?