The language contains some design errors, some of which have been corrected during the course of its evolution, some have not... It's probably now the world's most popular programming language, if you consider all of the platforms on which it has been deployed. But the language has problems, and we will look specifically at those problems.
It had initially some bad implementations, and the language has received a bad reputation because of those implementations. The implementations have gotten good. Very good, in fact. But the reputation of the language has been damaged.