has problems in language and sentence structure that result in a lack of clarity
contains occasional major errors or frequent minor errors in grammar, usage or mechanics that can interfere with meaning
Moreover, another assumption in the argument is the causal relationship between hours of sleep per night of executives and the success of their companies.
这里assumption is relationship的搭配是有问题的。因为assumption是指假设某件事是成立的。所以这里可以改为
Moreover, another assumption in the argument is that there exists a causal relationship between hours of sleep per night of executives and the success of their companies.