RE: Question about ocassional loud/crazy arrow flight.
Of the QADs that I've installed, when installed on certain bows with short cable slide travel and faster speeds, will NOT drop fast enough. If you're using vanes rather than feathers, it's more pronounced. The spring tension can be increased and will most often correct the problem, but it is a cumbersome job.
This may or may not be your noise, but it's a start.