This is a bug that has been fixed in a pre-release version that is not publicly available. It had to do with compatibility with the legacy RCX which originally did not have an opcode to except run-time frequencies.
If you send me an email to firstname.lastname@example.org
I will provide you with a link to site where you can download this pre-release. Or you can wait a few days and it will be available on robotc.net.