Command Output Is Not Redirected to File

I want to execute the following command, which is related to Rational ClearCase. The output of this command should be redirected to the file testout.

Command

rgy_check -vobs > testout

Output

rgy_check.exe: Error: An unregistered region \<region> was found in
VOB tag entry.
rgy_check.exe: Error: An unregistered region \<region> was found in
VOB tag entry.
...

The file testout is created, but somehow the file is empty.

Grep also doesn't work, it still gives the original output

rgy_check -vobs | grep "06a89"