I had a similar issue with my first module. Most of the time, the sliders would do the trick, but sometimes, it would just take about 5 minutes for the sound to start coming through. Then it got to be about 10 minutes. Couldn't deal with that in a gig setting!
I had my module replaced under warranty. It was pretty soon after getting the kit. My replacement has been going strong for about a year and a half so far!
Alesis customer service was always very good to deal with for me.
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Shawn