Created attachment 120422 [details]
A selection with an unintended spike.

SUMMARY
Sometimes when I use the Outline Selection tool and don't finish the outline manually (not sure how else to describe it), it will create a "spike" in a random direction between the start and end points. This does not happen all of the time, but it does happen both when using a mouse as well as a graphics tablet (an XP-Pen Deco 01).

STEPS TO REPRODUCE
1. Select the Outline Selection tool and select a portion of the document
2. Leave a gap between the start and end point of the selection when lifting the stylus pen 

OBSERVED RESULT
I have included an attachment of the spike effect. I have highlighted the area of the selection that I intentionally created. I have tried both the latest stable version, as well as Krita Plus (git 98d97d0) and they both have this same issue, though I think Krita Plus does it less often. I am running Windows 10.