I've also had many one-time gremlins, including the dreaded speaker full-blast mentioned here, but in my case, it happened while driving, when I tried to lower the volume while switching from FM to CD (trying to avoid a blast from volume differential, ironically). Never happened again.
Problem is this stupid car fires everything on the moment a door or trunk is open. Plus leaves everything on for several minutes after shutting everything off. You can always hear the speaker static if you put your ear on the front tweeters after turning engine off. The static is always there, but mostly unobtrusively. It's either the head unit or amp. And I bet most of these cases is with the EPS, which I have. Haven't heard this happening on the HiFi standard system. As long as it doesn't happen again, or more often, I won't worry about it. But I'd LOVE to know what the hell can cause that. I doubt it's a bad ground, but could be wrong. It's a head scratcher. Have a good one folks.