I am learning English as a second language. I was going through the feedbacks of examiners, who conduct/mark CSS exams (this is a competitive exam conducted to appoint Government officers in Pakistan), as to how a good essay should be written. Also, they are pointing out the mistakes which aspirants (who have previously attempted this exam) have made, and I and came across the following text which sounded to me to be having some sort of disagreement in overall structure.
The first part of the sentence contains “to be” verb and the other part contains past participle (substantiated). I want to learn whether there is a flaw in the given structure or it is just me who’s not understood the English language yet.
The candidates were neither able to build an argument from multiple angles nor substantiated it with facts.