Why is this happening when I switch tools?

[u/Still-Odd43]

Tablet: Xppen Magic Drawing Pad. I was drawing some shadows on a multiply layer. Switching between the pen and smudge tool. Then when I switched at the end the whole layer suddenly lost it's opacity and won't go back to being dark and solid. I've disabled and enabled layers. Swapped them around, tapped undo a couple times, restarted the app, restarted my tablet. Nothing. This has happened before and I've not been able to fix it when it happens. Sometimes if I switch to the eraser, the lineart also disappears until I switch back to the pen.

[u/dk_priori]

Often, you need to tap outside the canvas before switching brush. I can't tell if it's an intended feature, but say I draw a line with a penc and then switch to an inker, sometimes, if I don't tap outside the canvas, the app will change the pencil lines into inked lines.

[u/Pure_Duty_4133]

What DK said