V3.9 Batch Master Issue

In previous software versions I was able to set the flash key on a playback rate bath to flash to 0 and it would "freeze" the effect then when I unlatched the flash key it would resume. since upgrading to 3.9 this feature appears to be broken. I have tried all the different mapping options, including Halt, flash at 0, flash intensity at, etc. Is this a bug or has the syntax changed?