The grammar errors are based on the rules of antecedence. The first phrase is antecedent to the subject of the sentence. Thus, the investors were the ones disappointed. This error is so common, it has become almost a cliche in grammar tests. The second rule here is that a pronoun refers to the first noun prior to it. So, its refers to company. In terms of style, it is actually desirable and parsimonious to use the pronoun, and not repeat the noun again. The final error is one of logical antecedence:
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