Peter writes that there were things in Paul's Epistles that were hard to understand:
2 Peter 3:16 As also in all his epistles, speaking in them of these things; in which are some things hard to be understood, which they that are unlearned and unstable wrest, as they do also the other scriptures, unto their own destruction.
The perspicuity of Scripture does not mean that all things in the Bible can be or will be easily understood by every believer. Paul understood things in the Scripture that he wrote that others found hard to understand.
God does not give all believers illumination about His truth equally. Those who immerse themselves in His Word will be given treasures from His Word that others who do not immerse themselves in His word will not be given (Prov. 2:1-9).
To think that everything that is important in a passage will be and can be equally understood by anyone who reads the passage is to hold a defective view of interpreting the Bible. Even extensive study of a passage by multiple students of Scripture does not guarantee that each one will understand what's in the passage equally well.