Wrapping bug when appending in block visual mode

[baffalop]

When visual block is selected which reaches to the end of the selected lines, pressing A puts the insert cursors at the beginning of the lines, shifted down one line. I'm guessing some kind of soft-wrapping behaviour is kicking in when it shouldn't, or the position is overflowing to the next line.

Example

With a visual block selection on lines 64-71:

After pressing A:

Expectation: cursors at the ends of lines 64-71
Actual behaviour: cursors at the beginnings of lines 64-72

After typing a character and returning to normal mode:

Environment

Onivim Version 0.5.9-nightly (0.5.2198)
macOS 11.2.3