I checked the second page of Pattern Review. One of the posters said to contact Singer support. There were quite a few owners of this machine that posted, so it must be a problem with this model. Anyway, one of the posters called singers 800 number and they told her to take it to a Singer warranty dealer. It so happened that she was in California and the dealer was in Idaho. So she gave up on that. There was no resolve in the other postings. I would call Singer and tell them, there seems to be an issue with this model, what can they do to help fix it. Sometimes vacuuming the connection on the machine helps with this issue. I had a problem years ago with a New Home (Janome made) machine, cleaned the connection hole and the foot pedal worked.
Another time, I took apart the foot pedal and found carpet fuzz inside, cleaned it out and the foot pedal worked. Be careful if you take apart the foot pedal, there is a spring inside with some models and the spring will go flying across the room. ask me how I know.
Call a Singer dealer and talk to their technician. Ask him what he thinks it could be and how much the cost would be to fix it.
It would be highly unusual if you had two foot controls be bad....but I guess it could happen. I would ask the technician if they have a foot pedal that works on your machine that you could test with. Best wishes in finding an answer.