Intermittent Problem

Sub plays for a while, then stops, then plays again, sometimes several times within the same song. Sometimes makes a <static> sound as it fades in and out of play.

I opened it up and sure enough, the plastic bracket retaining the heat sink to the enclosure had snapped. I felt that this could certainly be related to the problem (everytime the bass would crank the heat sink would viobrate pulling on the wires) so I pulled on the wire and found that 1 of the 4 connections was a bit loose. I fit it back on, fixed the retaining clip and remounted the heat sink to its perpendicular position - feeling that I surely had fixed the problem. Not so.

The device gave me about 15" of trouble free playing, I was convince that it had been fixed. I played the 3 songs that seemed to <irritate> the problem the most:
Lovers in a Dangerous Time (Bare Naked Ladies), Temperature (Sean Paul) and Fly Away (Lenny Kravitz). The sub failed midway the 3rd song.

I was certain that this was a mechanical problem, one related to the vibrations of the speaker causing a loose connection somewhere. However, I'm not so sure anymore, I'm starting to think that this may be a heat problem. The vibrations in the first 2 songs were much more deep that those of the 3rd. However, the bass is working overtime with Lenny, it's constantly going and this seems to be what is triggering the failure. but if its a heat problem, why does it fade in and out and why the <static> sound? Could it be a cold solder? If so, how do I locate the failure point?

Any suggestions?