Pattern Pad lighting behaviour with Program Changes

I cannot work out why the following occurs. I have a track with several patterns. The associated patterns only contain Program Changes. (1 per pattern). They all work great and in fact I have several other tracks that perform the same function.
For some reason I cannot understand, P1 is not lit like the rest of them (it remains dark), even though it contains the same information. I notice all the others have CC information indicated in the track display, (There is no other information on any of the patterns other than a Program change), P1 does not. The same thing is happening on other tracks as well with a similar setup.
I have tried to delete the tracks and start again - exactly the same thing occurs. I have searched the manual and can find no reason for it.
As i said, it all works well, it is just curious and annoying.
Any help would be appreciated.

yeah the same is happening here.
Check my similar report Track PC + bank (recording slight misbehaviour)