'Lock Transparent Pixels' and Layers Problem

Hey there Photoshop community,

I wanted to ask if anyone knows how to fix this problem I am having. I have been using the 'lock transparent pixels' feature in the 'layers' tab to isolate my line art so that I can color over it to change it from black to blend better with my drawings. Just yesterday after finishing one drawing and moving on to another it seems to have stopped working. First of all, if 'lock transparent pixels' is on it either doesn't color (if the line is opaque black) or if it is somewhat transparent it only colors it as if it was 'burned' (color is very dark and doesn't replace the black line but goes over top/underneath of it). If I try to use the 'lock transparent pixels' and then turn it off, then it does not let me draw over the black normally and only draws underneath the already existing black lines. This is with the same layer as the lines selected, but it is as if I am now trying to draw on a new layer that doesn't exist. I don't know why it suddenly started doing this. I have tried updating Photoshop and restarting my computer but the problems persists. Any way I can fix this?