sub cuts out when I accelerate from a stop

I have a pioneer sub hooked up in my 2008 wrangler with a built in amplifier. Done professionally. Occasionally when I accelerate the subs cuts out for few seconds. The blue light stays on. It will also do it in park when i rev the engine. I had them check thier work and he says its the preouts on my stereo not the grounds. Is that possibe? I just need some opinions before i drop 300 on another head unit.