Is there a temperature or moisture difference?

Not really - they both are consistent.

IF food is identical in type & quantity and temperature and moisture are not any diff from tray to tray then there should not be a problem.

The 360 is designed for the worms to move easily up and down thru the bins. If they are going down when they are normallyup then something is not to their liking in the bin, you need to figure out what it is. The worms should be happy if the temp is between 50-80 F. There should a balance of greens and browns too much green could cause the bin to heat up. Another remedy might be to put a layer damp newspaper on top of your upper bin bedding.

I currently have 3 working trays and 4th with just dry paper to deter fruit flies, before that I had 4 working trays but Im now using 3 . . The system seems to self regulate itself production and moisture wise and am quite happpy with it. I dont have any liquid drainage at all with mine. Ive been running the 360 for at least 3 yrs. I have even taken some worms from it and started another bin with 10 gal rubbermaid and that bin seems to be doing well too.

I was having that problem too with my 360 about 3 months into starting the bin. I also thought there was a decrease in worms (they were unwilling to stand for a proper head count so I was just left with that impression). After scouring all the information I could find in these forums, I determined that my food amount, bedding, and moisture levels were where they were supposed to be.

I ended up fluffing the top bin and keeping a closer eye on the temperature. I also stopped putting in kiwi peels thinking it might have made it too acidic (although they'd been eating them just fine). In addition to all that, I started really smashing up the food better and let it sit a little longer before I put it in the bin. I'm not sure which one of those actions fixed it, but two weeks later, the work strike seems to be over as everyone is back to munching microorganisms in the penthouse.