The english "reads" implies a singular subject when the answer "legunt" implies a plural one...
Yes surely some mistake. Did the Romans have many female doctors?
Does multos exclusively appear before the noun it's modifying? As in, "medica libros multos legit."
why is not correct to write "medicus" instead of "medica"?
As long as everything else was correct it should have been accepted. Report it, with the flag, should it happen again.
Multos libros and not Libros multos ?
The gender of the doctor was not specified so "medicus" should also be acceptable.
Latin is more free regarding word position, so I am surprised that libros multos counts as wrong. It is not. It is just a matter of style.
Why do you not accept ,,medicus " ?!