It sounds like an intermittent connection issue with those sensors. Perhaps the wiping action of disconnecting your old sensor and connecting your new sensor cleared enough crud from the harness contacts to read the new sensor for a while. But if the harness contacts were pretty dirty/corroded for some reason perhaps it's now causing intermittent connectivity issues with the new sensor? Maybe clean/check the contacts for those sensors at the harness end. Or maybe even the harness itself (vs its contacts) is starting to develop intermittency issues?