The skin modifier is incorrectly applied to the skeleton I'm new to Blender and I ran into this problem, when I trying to skin my handrail skeleton (a screenshot of the skeleton is attached below)

But after applying the skin and trying to reduce it(by pressing the keys CtrlA), a certain part of my handrail becomes much thinner than the rest, even at this stage it is clear that the part that is closer to the top is much smaller than all the others (the screenshot is again below)
Select vertex and check Radius in Properties side panel.
Your issue looks differently, probably two vertices (or split).