Fx6 making thumping noise

I've had my fx6 set up for about 3 months now, and I keep having issues with it making a thumping/knocking sound. Most recently, I just took it apart yesterday because it was making this noise, took the impeller out and wiped out any gunk in there (there didn't seem to be any sand or gravel in there), and rinsed all of the media (in primed water). Today it is making the sound again. I unplugged it for 5-10 minutes and then plugged it back in and it's no longer making the noise. Has anyone experienced this? Any suggestions? I don't mind unplugging it for a few minutes but that doesn't always work. And like I said I don't see anything in the impeller area. I use black diamond blasting sand with a bit of aquarium gravel mixed in (like a few pieces here and there) and it's a 120g tank. TIA!

 

Maybe a piece of Bio media getting sloshed around and knocking the side of the basket?

That's strange.

 

Maybe a piece of Bio media getting sloshed around and knocking the side of the basket?

That's strange.

My bio media is all bagged and doesn't really touch the edges of the basket so I don't think that's it :/

 

I've contacted fluval and they want pictures of my setup, they think there may be air getting into the canister. I'm worried they're going to tell me it's because we're not using the hosing they supply (we've switched to a combination of tygon and pvc). Here is a video of the noise. It should also be noted that I am able to make the noise stop by lowering the flow, which is demonstrated in the video as well.

 

Is the hose rattling next to something?
If you grab the hose does it stop?
Are you using the rubber feet on the bottom?
Is it level?
Are you sure the impeller is seated properly?

 

Is the hose rattling next to something?
If you grab the hose does it stop?
Are you using the rubber feet on the bottom?
Is it level?
Are you sure the impeller is seated properly?

-Hose isn't rattling next to anything
-Doesn't stop if I grab the hose
-Yes, using the rubber feet on the bottom
-It is level
-Pretty sure the impeller is installed correctly, I'm going to take the filter apart later so I'll check again.

It feels strongest when I have my hands on the actual canister, not when I touch the impeller housing or the hoses. Sometimes it stops after I clean the filter, sometimes it stops when I unplug the filter for several minutes then plug it back in. Sometimes it starts right back up or is worse after cleaning the filter. I'm at a loss

 

Update: took the filter apart last night. We drained it almost completely before moving it. The impeller was installed correctly. Once we started taking it apart I noticed my middle basket where I have my polishing pads was holding water. We had 3 polishing pads (50 micron) stacked on top of each other. I think what had happened was that the filtration was too dense so water wasn't able to pass through it properly, which could have potentially been trapping air as well. I left 1 polishing pad and reassembled the filter and when we plugged it back in there was ZERO noise (aside from the normal light hum). This morning there's still no noise so I'm pretty sure that was causing the issue.

Bwood22 thank you for taking the time to try and help me solve this issue!