Strange 293T seeding - (Feb/08/2017 )

Can anyone explain to me why my 293T cells are setting down in the pattern of the rack???  This has never happened to me in previous labs.  The plates are falcon and my incubator is new and made of copper.  This is not conducive to lentiviral production and I greatly appreciate any help. 

This is usually caused by temperature fluctuations. 

Google Corning cell culture troubleshooting guide, it'll tell you more.

WOW!!  Thanks bob!  It's very obvious that this is precisely what is going on.  It must be the copper racks that hold heat much better than the aluminum.  It seems odd that I'm only seeing this in the 10cm plates (not flasks or well plates) but I really can't tell you how happy I am to have an answer!!