Lens correction causes offsets in mask creation
After lens correction has been applied, in any other module the mask creation will suffer from an offset proportional to the amount of the lens distortion. I applied lens correction as one of the first modules, but after realizing this behavior I am going to change this, and use lens correction only after the modules that use masks. The only problem with this workaround, that the mask is not distorted with the image if the lens correction is applied.
I don't know whether it should be classified as a bug, rather as a feature request, to calculate the mask distortion based on the lens correction to always have the correct mask position and shape disregarding of the applied lens model.
I am currently running Darktable 2.6.2 on Ubuntu 18.04.2 LTS with Gnome DE on 64bit Intel HW.