I just want to make an observation. I develop VSTs as a hobby. As part of the development cycle, I need to test them in various DAWs, like Cubase and Cakewalk Sonar. In testing a synth I developed, in Cubase, if the test doesn’t go well, Cubase simply crashes when i try to load the synth as an instrument. However, in Sonar if there is a problem with the VST, on startup it will give me a message saying there is a problem with the VST and ask me to disable it. Once disabled, Sonar will then continue to startup as normal, I just can’t load my VST.
So in my opinion Sonar does a much better job of handling misbehaving plugins. Maybe we need Cubase to handle misbehaving plugins better.
Just want to mention that Cubase overall is a much better DAW than Sonar and is my goto DAW.
You might want to type “what are the trade-offs when sandboxing vst plugins in a host” into your favourite search engine.
And maybe consider using another host in the early stages of plugin development and only start testing with non-sandboxing plugin hosts once plugin crashes are very unlikely.
Cubase will of course also scan/load a newly detected plugin on startup and if it detects some issue or the plugin crashes, it will be put on the black list. This is done in a separate process already and won’t crash Cubase. Seems like similar behaviour as you describe with Sonar, just that your plugin for unknown reasons passes the initial test in Cubase but not in Sonar…
Apart from that, a quick search seems to indicate that Cakewalk also uses sandboxing only when scanning, not in "“production”, just as Cubase.