Incomplete spectrum at the edges of the data cubes are not processed by ZAP, since they have too many NaNs (ZAP filter out spaxels with more than 25% of NaNs). Because of this the zapped cubes contains edges values strongly positive or negative, and this propagates in the combined cubes.
We could provide a script or an option to remove these edges, I already have something for this somewhere.
Incomplete spectrum at the edges of the data cubes are not processed by ZAP, since they have too many NaNs (ZAP filter out spaxels with more than 25% of NaNs). Because of this the zapped cubes contains edges values strongly positive or negative, and this propagates in the combined cubes. We could provide a script or an option to remove these edges, I already have something for this somewhere.