That is related to AESH-497 but completion is not involved. By simply typing some character in the middle of a command (content that makes the command to be longer than the terminal width) the cursor jump, the character.
From this point, the command content and cursor are desynchronised, the typed content is internally added to the right position but display is broken.

To reproduce (aesh example):

• ls <long path that is size -1 terminal width).
• move cursor backward.
• type some text ==> cursor jump

This can also be observed with commands longer than the terminal width (spread on multilines). If the cursor is located in the middle of any line and the added content makes the line to be longer than the term width, the cursor jumps at the end of the first line (whatever the current line is).