Hi H4voc,
The fix for the reported fault is included in the latest developmental build (L3DT Pro 15.04.0.1), which is on the pro downloads page now (please see sales/reg receipt e-mail for link). Please let me know if you find any further problems. Thanks again for the bug report, and for your patience.
If i change 1 or x tiles in the DM and recalculate the HM does it calculate the whole map or the edited part only?
At the moment, the whole thing is re-calculated.
It may be possible for me to make L3DT re-calculate a selected area and then blend the result with the existing heightmap, but it's not going to be easy or quick. The problem is that changes to a single design map pixel can have far-reaching effects across the heightmap, particularly when strong erosion is used. This means I may have to re-calculate much more than just the heightfield area corresponding to the modified design map pixels; I'll have to re-generate a larger area depending on the settings used. Also, a better blending algorithm may be required than what I currently use.
If a change a generated heightmap via 3d brush, does the DM saves this changes too?
No. There is no easy way to do this automatically, as the DM->HF calculation is not reversible without significant data loss.
That said, you can re-generate the whole design map from the heightfield using 'Operations->Heightfield->Generate from DM', but the result is an approximation, and it certainly won't give you the same heightfield as the original if you go ahead and re-calculate the heightfield.
Best regards,
Aaron.