Hi, new Cubase user here. I just encountered and solved my first major problem, and thought I would share my experience in case others are having the same trouble.
I was trying to play a VST from my MIDI keyboard and a Breath Controller which were both sending information through different physical MIDI ports on my interface. After 10-30 seconds of noodling I would get weird stuck notes - Weird as in they wouldn’t be lit up in the VST GUI, but were still sounding, as though the sustain pedal was down (it wasn’t). After some poking around on the forums I found out that Cubase apparently doesn’t like MIDI streams from multiple sources at the same time. The workaround to my problem is therefore to merge the two MIDI streams in MIDI-OX (a free MIDI utility for Windows) and route the resulting stream back to Cubase using the LoopBe1 virtual MIDI driver (also free for non-commercial use, and very cheap if you need to buy the license).
I am glad I got this solved, but I have to say I’m a little surprised that something this simple was a problem at all.
This forum thread helped me solve it: