I've never heard of a 416 doing this and browsed a few pro audio forums with no one reporting it.
I'd recommend a trip to the mothership (i.e. back to the factory for an overhaul) to repair the problem.
If you live in or near a major city, there are pro audio shops such as Trew Audio, Professional Sound Services and Gotham Sound to name a ferw that may be able to help.
You can also try posting this question on http://jwsoundgroup.net/, a forum for audio professionals who do this for a living and see if anyone there has any other suggestions.
Mike
