4gl RDS 7,2 on hp-ux 10.20 -- string handling errors

A warning to others and a plea for ideas or help. Just upgrading to 4gl RDS 7,2 UD4 running on hp-ux 10.20 and I'm having problems with simple string handling causing errors. Is anybody else having similar problems and have they managed to determine what is happening ? Example 1 LET a_string = 'Some data to be displayed somewhere' LET b_string = 200 SPACES LET a_string = b_string[1,22], a_string caused a core dump - replace '22' by '21','23','24' - core dump. Replace by 20, 25, 26 - no core dump. Move code to a small test program - no core dump Example 2 A LET command of the form LET m_str = m_array[1].str was causing the string m_str to be truncated to 10 characters (even though both sides were defined as CHAR 80 .) Changing the code to LET m_str[1,80] = m_array [1].str fixed the problem This problem also disappeared when the data was moved to a small program. Naturally this code works fine running under RDS 4.14 Informix can't help because I can't reproduce the problem in small programs. They have 'no known problems' of this nature. Anyone else experienced anything like this ?