System Information
Operating system: Linux-4.15.0-46-generic-x86_64-with-debian-stretch-sid 64 Bits
Graphics card: GeForce GTX 760/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 384.130

Blender Version
Broken: version: 2.80 (sub 50), branch: blender2.7, commit date: 2019-03-18 21:39, hash: rBd47f827019f2

image texture mapped as stencil in texture paint mode unable to be adjusted after using an image texture mask mapped as stencil

Exact steps for others to reproduce the error
from the default start up
with the default cube selected, switch to the "texture paint" workspace
add a new texture paint slot ( base color)
create a new texture brush and make it an image texture, load any image.
change the mapping option to "stencil"
it can be adjusted (rotated, moved or scaled) with the right click
remove the texture from the Texture Panel, and load it in the Texture Mask panel, change the mapping to "stencil"
it can be adjusted with right click + Alt
remove this texture from the texture mask panel and load it again in the texture panel
the image in the viewport is now unable to be adjusted.