Graphics: transparent lines with bezier curves have overlapping area at join

When two lines (with alpha = 0.2 or something <1) are thick, and close together, with a bezier curve connecting them, and you try to join them, the behavior will be strange but understandable (see the attachment)

Just wondering whether there are some work arounds? Thanks in advance!

Here's a running example:

PixiJS v5 Line Join and Line Caps - JSFiddle - Code Playground