Reason's BV512 Digital Vocoder rack device always had a very useful behavior regarding its use as a MIDI-to-CV utility device.
Before the Kong Drum Designer rack device, which is typically the easiest and preferred device to convert a MIDI Note (i.e. Pad hit) into a CV Gate output (each pad has a CV out gate at the back) the BV512 Vocoder was the only rack device offering a similar behavior.
The BV512 MIDI Implementation made it respond to a range of MIDI keyboard note input to control each of its 32 Vocoder Bands. This allows various cools tricks related with directly controlling specific and multiple bands while in Vocoder mode.
The 1st 16 of those Vocoder bands, when activated (either by audio modulation or MIDI note input) will have their respective value output as CV at the back of the device.
BV512 did its CV tricks tirelessly, no matter if there was an audio cable connected to the modulator audio input or not. It even worked perfectly while the "Enabled" switch was Bypass or Off.
Well... guess what? Apparently, allowing Vocoder Band control through MIDI input when there's no cable connected to the modulator audio input was... "a bug" (kinda).
This "bug" was fixed in Reason 7 ...so, yeah, you guessed it: Any Song or Combinator patch relying on the good'ol BV512 original behavior changed from a state of "coolness" to "borkedness".
Yeah... there are some patches that worked fine up until Reason 6.5.3 that now stopped working in Reason 7.1.1, Reason 8.0 and Reason 8.1 (and so on...)
Is there a solution?
Either replace the BV512 acting as the "MIDI Input" device with a Kong, having then to deal with all the CV rewiring needed and Combinator modulation matrix (re)configuration or... simply connect a dummy cable to the modulator input