Bug happened again, but now I did just small edit so I remember what I did. I loaded same file from backup again, repeated the edit as before in same way - no bug.
Looks like the bug is not dependent from the editing actions. Here is what the bug changed: (viz https://images2.imgbox.com/db/82/5sHv6a9P_o.png ) -- <https://forum.pspad.com/read.php?4,77267,79611> PSPad freeware editor https://www.pspad.com
