Hello Alex, I'm not in the forum much these days but I hit the same bug that I think has afflicted you, and bounced in to say something and catch up in other ways. Now, I'm not on Notation staff or linked in any way other than a user, so all of what I'm saying here is Me not Them (!)
I am using Notation Composer for professional/commercial composition now. I am still using it for the same reasons I welcomed it in the long, long ago: there is no other piece of software that can do what Notation does at anywhere near the price. So I put up with the buggies.
I write, perform and record. The particular aspect of Notation Composer that is an incredible winner here, and where no-one else even looks in, is the deceptively simple as-notated/as-performed/combination using notation and the piano roll together. This was not available in early versions; when it arrived it trailed a few remaining bugs, which were quickly stepped on.
I know there is an active community of what amount to beta testers. The updates come fast, especially in response to a new bug. At the same time, the new bugs appear because the capabilities keep expanding with each update.
Right now I can't afford to have things fall over, no time (!), so normally I run an update or two behind the current, and let the enthusiastic checkers clean things up. This is not optimal, of course, and it would be preferable to non-enthusiast users if the testing could be separated from the commercial product, as you suggest.
But I bite my tongue, because I'm aware that Notation Composer is not a huge Cakewalk-type organisation but a couple of people, which again is reflected in the pricing.
From past experience, I predict the bugs which bit us both will be fixed in (literally) a few days. Even with the passing bugs, the product to me has been worth every penny I paid for it.
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