A flashy produc that crashes when you're using it might as well not be used at all.
Having used both, I now use OzRunways exclusively, due to the stability issues you've experienced yourself. I have managed to crash OzRunways once or twice in the years I've owned it, but it is light years ahead of AvPlan in that regard.
For tech support, I have asked a couple of questions here on Prune and that's been it. I haven't needed to contact OzRunways offline at all, and they're quite responsive to their thread here, so for me that has been sufficient.