hi folks, a similar problem was happening my end...
it went like this
in at5 when using both an audio interface (for outputs) and a stomp I/o as input and controller, these crashes would happen constantly to the point where it is unusable....
so I tried all of the above total clean reinstall a Mac OS reinstall etc, but it still happened..
I solved the issue by using my audio interface for input and output settings, and setting the stomp I/o to controller via usb..
or I can just use my stomp I/o for input/output and control.
for some reason at5 seems to get a bit scrambled when having the input set to a different source than the output
this has solved the issue for me..
it may help some of you guys also, again it may not be a fix for you but maybe worth a try..
hope that helps someone
cheers
Craig