When i select a brush, and then change it's size via widget in toolbar, the brush suddenly changes it's brush tip. 
The point seems to be that Krita for some reason remembered, that some time ago I selected one of tags in brush tip selector in brush editor dialog; and now, when I change brush size, it recalls that and selects first brush tip with that tag.

I checked ~/.config/kritarc and found

[SelectedTags]
kis_brushes=Comics
kis_paintoppresets=Expressionism

The "Comics" is that tag, first brushtip with which krita tends to select each time I change brush size.
When I remove "kis_brushes=" line and restart Krita, everything goes back to normal.

Reproducible: Always

Steps to Reproduce:
1. Select a brush preset.
2. Paint with it a bit
3. Go to brush editor, under "brush tip"
4. Select some tag other than "All"
5. Select one of brush tips.
6. Paint with resulting brush a bit.
7. Switch to another brush preset. Note that it paints as expected.
8. Change brush size by using widget in toolbar, for example
9. Paint with brush

Actual Results:  
Brush continues to paint with the same brush tip

Expected Results:  
Brush starts to paint with first brushtip from tag you selected in step 4.