I also started on the Humira/methotrexate combo but the Mtx began to impact my liver enzymes so my Rheumy began to lower the mtx dose and then from oral to sub-cutaneous. Once he lowered it again it was too low to prevent me from developing Humira antibodies - so I had to drop Humira and switch to Enbrel.

I bore you with all that to suggest that some of your breakthrough events may be because your body is developing antibodies to Humira.