Why do you use Galacticraft Oxygen anyways? That is not really meant to work anyways. With GT Oxygen everthing works, so there is no bug...
If you absolutly want GC Oxygen to work, i will add a recipe balanced to its production costs.
The GC devs have stated that GC oxygen is actually air and should not be dictionary compatible with any mods' pure oxygen, so I would advise against this (although for this discussion the point is moot anyways).