Not really anywhere to send them where they’re guaranteed to be looked at, but you can post them in the issues section and it’s just possible a moderator will pass them on. You can also phone up the official Steinberg support line, they will help you with any problem and provide you with advice as to how to fix it.
One thing I’d say is that you make sure you have the latest drivers for everything, particularly the latest Motu drivers and graphics card drivers.
I have the 424 card myself and I’m fairly sure it causes blue screens and lock-ups because when I swap to using another audio box (m-audio profire on firewire, which I use for simple sessions sometimes) I don’t experience any blue screens. That said, I’m on the latest drivers and it still BSODs. Perhaps you could try a session using another sound box output, or the inbuilt soundcard, just as a test?
Graphics card drivers were causing me display trouble the other day with the new mixer implementation. A moderator suggested this, I checked, updated and the problem went away. Not a crash, granted, but it solved a display problem, could be this is causing a crash in your system.
Also Antares Autotune has caused problems recently, although I haven’t had cause to use it for a while so I can’t say if this has been sorted. Melodyne I’m usually cautious with as well, I save before adding it. But it’s certainly the case that plugins cause some crashes. Again, VST2 plugins via the Steinberg BitBridge are probably the worst culprits. JBridge provides an alternative to BitBridge should you really need VST2 plugs.
This is general info, and it goes along the lines of firstly making sure that the system is fully up-to-date, then the troubleshooting begins by removing some things which may cause the trouble, and by a process of elimination seeing if it gets sorted.