Problem when too many points used

[balmaslo]

Hi,
I'm using py4dgeo to align point clouds from a defined area (a rocky area considered as stable terrain and present in each cloud, which allows to compare snow volumes at different periods). The point clouds used do not have exactly the same shape or density, but represent the same terrain, and both contain the area chosen as stable terrain. I can't explain why the algorithm works with a certain size of stable area, but diverges/bugs when this chosen stable area used for registration is larger. Do you know where this could be coming from?
Thanks in advance.