Compression is a process where the blend mixture is formed into a tablet as per the capacities of the tools.
There is no technical evidence given in books or journals that loss of a API due to compression or during compression process unless you have sticking problems where loss of total blend takes place.
I strongly reccomend how you are sampling your Granulation blends and how robust is your blending process and what type of Blender you are using?
Foremost thing you have to do is look your blending cycles, blending validation documents and time of blending.
As the drug substance is too minute due to activity of this drug substance , any sticking during wet granulation might result in loss of API. Secondly how is your HAPI is added during your wet granulation process–what I mean to ask is do you have a Human intervention or is it automated process?
How robust and how sound is your bend validation process technically?
I request you to carry out a Scale-Down study. That means take a pilot batch and test your process.
Regards