The MPX format summary task does not recognize "Yes" in summary tasks.
Tested with MS-Project 2000 (9.0.2001.0219 SR-1) German.
Probably it could be the language?
Sorry i dont have an English Project to test it, and so the attached error-message is also in German.
Tested with V1.0b1, btw there is no group for that.
error-message
Thank you.
I will take a look on this issue.
I have added missing group.
Looks like, not working in English also. I tried several free viewers, without success.