caesarii don't display right bend with a single or double flange.
in the file test20._a,select bend from node 10 to node 20,then select 1- Single or 2- Double type on bend spreadsheet,Exit from piping input.Then open test20._a,bend type field is null.

Using your file (above) I can not reproduce this problem. I can change the "single/double" flange field save the file, exit and return to find my setting. I can also exit without saving which causes CAESAR II to prompt me to save the file. As long as the file is saved, the setting remains.