I would suggest it's going to be a little difficult to tell what's going on during this pulldown phase: presumably that product went in at elevated temperatures, and there's a lot of it?
For blastfreezing of packed and cartoned meat, rapid air movement round individual cartons is an essential part of the process, and what we see is is an initial period which shows very little temperature drop (as the heat migrates out of the product) then a sharp drop once it is frozen. This is typically carried out with -20 to -30'C air and takes 1 to 2 days.
Stacking the same product in a -25'C coolstore (minimal air movement) will take weeks to achieve the same result.
I like @nanomonkey 's eutechtic solution in this setup, if a suitable medium can be found.