The behavior, described in detail below, is observed on multiple systems:

GNU bash, version 4.3.30(1)-release (x86_64-pc-linux-gnu) with libreadline.so.6.3

GNU bash, version 4.1.2(1)-release (x86_64-redhat-linux-gnu) with /lib64/libreadline.so.6.0

GNU bash, version 3.2.25(1)-release (x86_64-redhat-linux-gnu) with
/usr/lib/libreadline.so.5.1

---

1. Type text into a bash interactive shell, e.g., "0123456789"
2. Cursor left, e.g., move left two spaces so point is between 7 and 8.
3. Exchange point and mark with "C-x C-x".  Mark is now between 7 and 8 and point is at beginning of line (initial mark)
4. Type new characters, e.g., "abc"
5. Exchange point and mark.
 
=> The cursor (point) is improperly placed in the same absolute position where the mark was, not the logical location in the text.  In the example of (4), point is placed length("abc") to the left of where is should be.

Note: In the CHANGES from readline-5.2 to readline-6.0, a similar bug was fixed specific to vi mode.