I just ran a test and these COBSW settings work for me in both native code or managed code either by setting them in the app.config file as COBSW with +B-F-N or by passing them on the command line on the debug tab using (+B-F-N)
Try the following program and tell me if it works for you? The result should be that when run the RTS error 163 caused by invalid data in the move (CHECKNUM is on) should be suppressed and the text file myfile.txt should not contain the embedded nulls before each non displayable character.
$set checknum
program-id. Program1.
input-output section.
select test-file assign to "myfile.txt"
organization is line sequential
file status is file-status.
data division.
file section.
fd test-file.
01 test-record pic x(10).
working-storage section.
01 file-status pic x(2) value spaces.
01 myspaces pic x(10) value spaces.
01 field-1 redefines myspaces pic s9(5)v9(2).
01 field-2 pic s9(5)v9(2).
procedure division.
move field-1 to field-2
open output test-file
display file-status
move x"010203" to test-record
write test-record
close test-file
goback.
end program Program1.