I don't think inhibitor is the problem if you are sparging it down sufficiently with N2. I would vary the surfactant components and see how well dispersed the mixture is before initiating. Mix small volumes in 4 oz jars, shake them and see which takes longer to show separation. Quick separation means a less stable system.
Thank you, William! I have this supposition because here in the lab we synthesize the monomer (fatty methacrylate ester) and if I compare it with the "same" commercial product the level of inhibitor is 5 times higher...