windows 10, gtx 960 4gb.
Short description of error
Packed to file sculpting alphas randomly stop working without any reason. No visible effect on the surface from the brush. Sculpting, however, works still when not using the alpha texture that used to be working nicely. That always happens with all the brush textures at the same time.
Exact steps for others to reproduce the error
You need to have "automatically pack external data to .blend" setting enabled and the multiresolution modifier. Go to sculpting mode. Load different alphas and change them from the texture mode to no texture mode. Start sculpting. I was using the textures on anchored mode, but I believe it has no effect on this. At some point, the textures stop working when you repeat these steps. At least on my system that happens. Not sure if it means something that my packed textures used to be .PSD files.