I dont think it is a bug as it is standard MIDI multimode. One has to distinguish between patch and sound. The small display does not help. On the Rev2, patches do not have names only numbers. The name on the display is (as long as "Edit Layer B" is not pressed) the name of the sound on layer A. If you press "Edit Layer B" the name changes, but not the patch...
For example I have patch No 8 and on layer A is a sound called trumpet and on layer B a sound called strings.
If I send a program change on channel 1 I can change the layer A sound to piano. The screen reflects this change and displays "piano". If I send a program change on channel 2 I can change the layer B sound to drums. The display does not reflect this change (it is however visible when "Edit Layer B" is selected) but it is audible.
It is important to note that all these changes take place within Patch No 8. This number is always on the display. The program changes did not change the patch itsef, only the sounds within the patch. If I hit "write", Patch No 8 would be updated with a piano on A and drums on B.
This is normal MIDI Multimode and all my other synths operate the same way. Some do have a control channel. If a program change is received on the control channel, the whole patch is changed. The Rev2 does not have this functionality. A MIDI channel can be set and in Multimode, this is the channel for layer A. Layer B is always on a channel one integer higher. If the MIDI channel is set to 3, layer A responds on 3, while layer B is on 4.
The same in other words (cheers LPF83)
https://forum.sequential.com/index.php/topic,4704.msg47269.html#msg47269