ABAP Short Dump on append of a sorted table

Question

Why does my ABAP program short dump when I append a line to a sorted table?

ST22 Shows ITAB_ILLEGAL_SORT_ORDER

data: sorted_tab type sorted table of ty_tab with non-unique key key,
      line       type ty_tab.

line-key = 1. 
append line to sorted_tab.  "works fine" 

line-key = 2. 
append line to sorted_tab.  "works fine" 

line-key = 1. 
append line to sorted_tab.  "<==== Short dump here"

Answer 1

The program short dumps when appending a sorted table in the wrong sort order

data: sorted_tab type sorted table of ty_tab with non-unique key key,
      line       type ty_tab.

line-key = 1.
append line to sorted_tab.  "works fine"

line-key = 2.
append line to sorted_tab.  "works fine"

line-key = 1.
append line to sorted_tab.  "<==== Short dump here"

Use INSERT in stead:

data: sorted_tab type sorted table of ty_tab with non-unique key key,
      line       type ty_tab.

line-key = 1.
insert line into table sorted_tab.  "works fine"

line-key = 2.
insert line into table sorted_tab.  "works fine"    

line-key = 1.
insert line into table sorted_tab.  "works fine"

Note If you had a UNIQUE key you would still get a short dump because you're using the same key twice