Well I have a theory about that ...
see my post:
Campaign Grinding SM Spending Guide (maximized for fusion)
My theory is as follows:
The Modules Boxes were giving essentially 2 things bonus.
- a good power/SM spent output for fusion (semi-OP in contrast to the other boxes)
- due to them costing only 20000 SM you could spam buy them so you could change two important factors:
a) Each box you purchase increases a counter that makes a bonus Power kit more probable to be included in the box
b) Each box you purchase increases a counter that makes A MYTHICAL ITEM included in the next box 100% probable after many purchases (but obviously not that many so that was SUPER-OP if you count purchases you made )
Also there was a technical difficulty with the modules (due to spam buying) in your workshop display and inventory. If you had more than 500 items a message box "Please Wait" was shown and items were loading in the background.
I guess that this was heavy on resources both on system memory and data bandwidth for fetching the list.
You have to take into account that the same game can be played on both Computers and Smart Phones and
probably the insane number of items on the modules category made the game sloppy or non-working
on some systems... (probably the game freezes many people complain about)