I guess "seemingly random" would be the appropriate answer.
I'm only using NI Kontakt3 for the FX and vsts and maybe a couple of the cockoos FX like verb and a little tap acho. I haven't had the DAW installed and understood long enough to really lay into any serious FX and editing there-of.
I can't wait to get around the fumbling stages of this DAW. It's really very impressive and claims a lot of powers and abilities. But I can't keep myself from laughing about it for offering itself up as the next best thing since sliced bread where it can't even perform the simplist of opperations without a time-consumming glitch. HA HA HA!! I can't wait til I start experiencing all the other glitches every one else is experiencing!!
you want to know what most of the buzz about reaper is? it's the people behind it. while the other companies were/are dicking customers around in all sorts of ways, cockos was/is listening, being decent and fair, creating kickass software. before reaper, you had to get special plugins to even do sidechaining. hell, you couldn't even rearrange the order of plugins without a big hassle or get creative with the routing. i demoed sonar, audition, and settled on cubase for a while until i jumped on reaper. all of those daws crashed, sonar being the worst. i couldn't use most of the free vsts in cubase due to severe crashing. audtition, no vsts. reaper is stable, and if you take the time to learn how to set up your plugins in their own process (it's pretty simple), i doubt that you'll see reaper crash again. many plugins have bugs, and cockos has made things so that other companies plugins have much less of an impact on reaper's stability. when i first started using reaper, i and a lot of others were hitting the devs up pretty hard with feature requests, and often saw things implemented the same day, and bug fixes the same day. i've been pretty much set for a while, so i'm not as active in discussing features/bugs as i was back then. those guys are bug fixing maniacs over there, and the whole process is transparent. if you can show how a bug can be recreated, they'll fix it. try that with other companies, but don't hold your breath. also, cockos doesn't play the multi-version game. one version, no bs. after you've spent enough time in reaper to know a little something, you're going to see how stable, light, fast, logical, and feature packed reaper is. there's a lot more in there than what first meets the eye.
my suggestion to you for your stability problems is to firewall your third party plugins. commercial and free stuff can and often do have bugs, free stuff sometimes has more because those devs aren't spending as much time on maintaining the free plugs. do a search at the forum over there, check the manual, and if you still have questions, ask.