The Arp/MS/Porta display mode (p 114 in the ops doc) shows that on the performance home page you can now make portamento settings for both the performance and for each part.

But for the displayed perf (CFX + FM EP) if you press 'Prt On' for part 1 in turns it on for part 2 also and vice versa.
Even if you select part 1 the Prt On switch sets the state of both parts.

Other parts I checked don't do that - the setting (or change of setting) for each part is separate. I haven't been able to determine
what it is about that performance that makes it work differently than other performances I checked.

If I add CFX Stage as a 3rd part it's portamento switch is independent of the other two for part 1 and 2 but part 1 and 2 portamento changes still operate together.

Does anyone have any clues about why these two parts might be linked together regarding portamento? I'm guessing this
may NOT be a 'working as designed' condition but only Yamaha knows for sure.