I think I found out why - in the materials tab of the properties editor, whenever the "Dots Stroke" is locked the airbrush can not be erased. Even if the selected material is a solid stroke.
I guess it has to do with the way the airbrush works. This is very confusing however, why would the airbrush give other stroke type options when it only uses dots stroke anyway?

IMO the materials tab stroke selection shouldn't even be there. Such an option should be determined on the selected tool. If the "Draw" tool is selected, give me the brush options and that's it, no material stroke selection. Similar to the issue of the pain(t) bucket tool, whenever that one is selected it shouldn't be only usable when the right material "solid fill" is selected. That materials tab stroke selection seems redundant and only causes issues IMO. Make it tool dependent and have it begone.

I still cannot reproduce...I draw with Airbush using a dot strokes and I can erase. Do you have a test file?

You misunderstood. Airbrush can not be erased when dots strokes is locked.

i.e. you have solid stroke selected and all others locked, select the airbrush, draw, then try to erase it. You can draw with solid strokes but you can't erase them while dots strokes is locked.

test file here:

This is not a Bug... Airbrush has pinned the Dot Stroke material.

When you draw, the material is assigned to Stroke...and when you try to erase, the material is locked.

The eraser check the material used to draw the stroke, not what you have now.

Were you able to erase what you airbrushed? No? Then it`s a bug

I don't care if it works like a programmer intended, it does not work as it should.

• I did not chose the dots stroke (which is weird that it does that because when I want to use the fill bucket I HAVE TO swing over to the stroke section and tell the stupid tool how it should work MANUALLY by telling it to actually FILL, who would've thought??!?)
• I scribbled an airbrush stroke
• I can't erase it

that's clearly not as it should be [UNLESS YOU'RE ACTIVELY TRYING TO MAKE BLENDER HARDER TO USE THAN IT SHOULD BE, HMMMMMMMMM]

@Daniel L. Travieso (YPS) Antonio explained it to you in a way it is very easy to understand and you can test this for yourself. Open new 2d template, choose airbrush, create a line and erase it. It works.

In your file you have manually locked the dot stroke. Because there is another level of customization for the brushes, material locking that override your material selection (the same way you can override your material color with tint) you are always drawing with the dot stroke. This is even more apparent when you are using extended line brush library like this: https://cloud.blender.org/p/gallery/5f235cc297f8815e74ffb90b

You cannot simply lock material yourself so it cannot be erased and insist that it is a bug. It is an override that is on top of your lock setting.

Unless you would want to have situation where lock would also be preventing the drawing with that material.

I didn't know it would switch from the solid stroke to the dots stroke when selecting the airbrush - how would I know that as the user?

Blender has actively TRAINED me to lock stuff I don't want to use because it otherwise does things I don't want to do, i.e. layers and strokes.

Just like the Fill Bucket example, which drives me so mad. Even MS Paint is capable of knowing what the fill bucket should do but in Blender you have to manually fiddle with the intended function. But in this case for some reason it does it on it's own - which is breaking a habit. I commend that it does that, it's great, I can't wait for the day the stroke selection is GONE because it was replaced by whichever tool you have chosen in the first place. I choose a pencil to draw solid strokes, I choose a fill bucket to fill areas, I choose the airbrush to spray dots. So the airbrush is smart enough to know what it should do - great! It sprays dots! Cool! Then why have you trained me to have to do it manually with the other tools and lock everything else?

@Daniel L. Travieso (YPS) : you make a valid point regarding bucket tool - this too could be solved by default to have solid material pinned. It would clear a lot of confusion for new people coming to blender. @Antonio Vazquez (antoniov) what do you think?

But you are making an injustice to compare grease pencil to MS Paint. A fair comparison would be comparing grease pencil to vector tool like Illustrator or Corel Draw. And there you would discover tools are acting the same.

fair enough, although I made the comparison for simplicity and functionality reasons only. you select a color, you select a tool and you use it without further fiddling

@Daniel L. Travieso (YPS) The problem is that you are comparing pears with apples. The final result of the stroke is the result of Brush (How the points are created) and Material (How the points are displayed). In a pixel base software, this is not the case. In Blender you need to define both things at time to get the result. There are plans for Tools, not only for Grease Pencil but for other areas of Blender, to improve how this relationship is handled.

Anyway, always remember that we are working with Vector data in a 3D environment, not 2D pixel base data... and for you, maybe is looks similar, but really is a totally different world. Ofd course, MS Paint can do things we cannot, but this is true in the opposite direction too... Blender does a lot of things that MS Paint can't.

understood. when will that possibly be?

@Daniel L. Travieso (YPS) Sorry, I cannot tell you because I'm not in charge of that.