Yes, it’s definitely possible. It sounds like you are running into the same phenomenon Irene experienced when she was doing Feldenkrais work with clients prior to taking the SE training. She would work with them and they would get good results, but then everything would just go back to how it was.

This is what led her to discover and train in SE. It is the old trauma patterns that keep us going back to the old tensions. We need to release some of those old survival energies before the Feldenkrais work can be effective, so it sounds like leaving the Feldenkrais lessons for now, and continuing to explore the other lessons repeatedly, will be important. It also may be helpful to get some assistance via one-on-one work with a good Somatic Experiencing/Somatic Practice worker.