Ok, I find it myself. Its not a bug. Here is my solution:

I changed:
Code:
str_cpy(input_str, "#100"); // reset the input string

with this:
Code:
str_cpy((input_txt.pstring)[0], str_create("#100")); // reset the input string


I think for TEXT objects its better you work with pstring.

Errors are the engine of progress.

Version: A8 Commercial
OS: Win 7 64bit
Models: Cinema 4D