Of course Paul talks of examination of conscience. Examination of conscience is required for confession and the Sacrament of Reconciliation is integral to the Sacrament of the Eucharist.
To substitute it for discerning the body of Christ is the error.
We have the real presence in Holy Scripture, in the history and practice of the Church, in the writings of the martyrs and Early Church fathers...
We even have it after the reformation until the sixteenth century and Zwingly.
Those who follow this error have lost the discernment of the body of Christ. And Paul warns against this.
To not realize the real presence in the Holy Eucharist requires errors of interpretation, ignoring history and following a false tradition.
Read it in Greek. It doesn’t say what you were taught. Read it in context and what it literally says ties the whole passage together. No fathers needed or early Protestants. Just God’s Word delivered Through the faithful Paul.