SVN r3655 should have this fixed, at least I can no longer reproduce the crashes here. I'm marking the slot-option related scan for changed device-instances as a 'critical section' internally now, so specific GUI operations are postponed until that section has completed. You'd usually use mutex'es for this, but both parts are running in the same thread, so it seemed more suitable to use a timer-based 'retry operation' approach.
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