Peter, the bugs you are experiencing are specific to the Yamaha Motif-Rack XS. To our knowledge you are the only one out of many thousands of Dorico users who have this VST plug-in, which creates MIDI ports when you instantiate it and which causes Dorico to freeze. The reason this causes a problem in Dorico 3 and not in Dorico 2, as we’ve explained before, is that Dorico 3 responds immediately to MIDI devices becoming available on the system, whereas Dorico 2 and earlier can only recognise new MIDI devices at start-up, so it’s impossible to reproduce the problem in the last version.
Although this is a bad bug and we do plan to fix it, there are many practical considerations that go into how and when a bug can be fixed, plus we have to consider the impact of the bug, which includes not only its severity but also the number of users who are affected by it. We fix dozens of bugs in every Dorico update, and take a very diligent approach to software quality. However, we cannot always fix every bug in every release, and in particular it may be doing a disservice to thousands of other users to devote a disproportionate amount of time to fixing a bug that affects a single user if that prevents us from delivering valuable functionality for thousands of users.
I realise it’s frustrating to have this problem. If you can avoid using the Yamaha Motif-Rack VST plug-in with Dorico 3 I believe you will find it otherwise very stable.