I did several attempts, loading separate bulks to slot 2 and slot 3, but the problem persists: the two PLGs get synchronized after several attempts.

Okay, I see you are describing a problem up until this sentence which seems to indicate that it ultimately straightens itself out... is that correct?

Fifteen years ago, I had everything about PLG150-series boards in my front "edit buffer", sorry but it has slowly been delegated to more remote regions of my brain. Are you certain both boards are PLG150-series and one is not the PLG100-AN? (Just a wild guess).

You may want to call Customer Support as they probably can still replicate your situation with actual gear. To my best recollection, once you set the POLY EXPAND to ON, the two boards became one and would do the right thing. The second board becomes just a slave to the first.

What is it you are bulking to the second PLG150-AN? The same material as to the first board?

Thanks Bad Mister for your reply. We're in the same boat, afterall. I left my S90ES unused for a long time, at least 5 years or more, so I my internal records are a little outdated. Although at the time I created an autoload file, I had the impression it did not restore completely the instrument as I remember.
It makes me laughing when I think that, in an italian music forum, I helped some people getting the most from a PLG150-AN 😀 And now I must start from scratch. 😀

By the way, I'm sure the boards are 150 series. The first PLG150-AN was bought as new, the latter as second hand, but the boxes and their content are the same.

I'm sure that the dumps contain the same data.

I avoid calling Italian Yamaha Customer Support because they are not up to give help.
Anyway, I'll get back into SNinety and read your articles to refresh my records.

Perhaps using also my old Apple Macintosh G4 will surely help a lot... 😉

Here's what I'll do, I'll put in a call to Customer Support here (USA) we have some great folks in there, all long time Yamaha people, between us we should be able to sort this out. I simply don't have any products that I can test this out on. No promises about the swiftness of the reply, because I'm running all over doing Montage introductions/trainings/events, so it may take a while, but I did understand you correctly that it eventually straightens itself out?

Again thanks Bad Mister! I can barely imagine the high level of psychological and physical stress this Montage storm is giving to you and your team. 🙂
Perhaps I choose the worst moment to put these questions about PLG150-AN 😀
I'm somewhat self confident that reopening old Studio Manager and AN Expert Editor files, stored in my faithful Apple G4, will refresh not only my memory but also S90ES'

As I wrote in the other thread I opened about S90ES Editor on Win7 32 bit, I partially solved the issue with the two PLG150-AN not in phase.
My mistake was to recall a solo, unison or monophonic patch, that can't obviously be played, by the two boards at the same time. When I recalled a polyphonic patch, Solina Strings, I could appreciate the full 10 voices polyphony, that's really exciting.
But, as I said before, the issue is not completely solved, because although Slot 3 should be slaved to Slot 2, this is not true. When I recall a patch on PLG-2, PLG-3 remains with the previous patch. This is not a great issue, afterall. Hope this behaviour will change when the two PLG will be moved on a Motif ES rack.