Rheem furnace code 44&55

My furnace low and high pressure switches close turning off the inducer motor. Sometimes the burners fire, but turn right off after 5 seconds and sometimes the burners fire and will stay on finally heating the house. Nothing is hot at touch and all connections are tight I’ve taken the inducer motor exhaust off to rule out any sort of blockage as well as inspected pressure switch tubing for holes or blockage. I’ve heard that the pressure switches are not likely to fail themselves and I’m wondering what other possible solutions I could try or if someone could verify that my pressure switches are indeed bad.