The white-filled circle arrowhead has some very strange geometry.
The white-filled circle arrowhead in Support Files/Resources/en_us/Arrowheads.ai has two doubled points in the black circle. This results in unexpected imagery when a path is given this arrowhead, expanded, and has further effects applied.
Screenshots: outline view, and outline view with half of each point pair selected and moved down 1pt.
This was discovered in 25.3.1 but I bet it's been lurking there long enough that it predates your current source control tree. :)