No, this is not "fixable" with brush settings.

I have searched for PS brushes the past days and looked at many. What surprised me (and I guess the original poster as well) is that many (many!) are "just" scanned brush strokes, as @LuckyClan correctly pointed out.

They are not meant for painting with them, they are just stamps you can use to put 1:1 to your picture. IMO this is useful only in rare cases, but of course your mileage might vary.

Because I had found so many of these stamp-only brushes when searching for free PS brushes to try out the brush import, I had assumed there were brushes out there, with a format not recognized by Artstudio. Seems that was not correct.

When searching more intensely, I found a good list of brushes for painting, which work quite well in Artstudio. For anyone interested, I am pasting a few links below. None of these are mine, all credits to the original creators.

https://www.deviantart.com/aarongriffinart/art/BRUSHES-609357781
https://www.deviantart.com/pixelstains/art/7-Charcoal-Brushes-for-Photoshop-523567502
https://www.gemistry.net/resources/photoshop-brushes/

Have fun.

So far it seems to me that '.abr import indeed is broken. I have yet to find any *.abr which can be imported to act as a reasonable brush. That the function itself is not crashing the program alone doesn't mean it isn't broken.

Were the brushes you imported successfully (which means working reasonably afterwards) 'in *.abr format?

You can see the issue yourself if you try e.g. the below free PS brush. The brush stamp of the imported brush is the sample brushstroke, which of course makes no sense at all.

https://www.brusheezy.com/brushes/56970-free-brush-stroke-photoshop-brushes

I have tried to import a few *.tpl brushes and they have worked OK.

For *.abr brushes I am seeing the exact same error.

Environment: iOS, iPad Pro