AFAIK some purchased Cubase 8~9 users on Audiobar forum were complaining that their Cubase occasionally quit without notice. I, as a purchased Cubase 9 user, had also met this issue. I initially think the problem is from Cubase itself, leading to my desicion of migrating my MIDI project to Studio One. However, I constantly met the rendering / downmixing corruption issue: the process occasionally stops with no file rendered.
I later talked to one of my friend who is an expert on how to build a computer for music production purposes. He suggested me to use Intel-branded SSDs in lieu of my current SAMSUNG 950 Pro (m.2 NVMe). Then I went to Calgary and bought a 1tb model of Intel 600p at Memory Express, put it on my Hackintosh in lieu of my previous one, and the Studio One downmixing issue had gone completely.
Even though I have no plan on moving my on-going work back to Cubase, I still think that the Cubase sudden-quit issue may be related to the firmware of the SSD worked for both the system and the project file. Thus, I leave this post here and wanna suggest Steinberg to do some compatibility tests with those SSD models on the market.