When characters were simplified, some Traditional characters that used to be distinct were merged into one Simplified shape. Going back to Traditional Chinese therefore requires a choice.
A well-known case is 后. In Simplified Chinese it can stand for the honorific 后 and for 後 ("after," "behind"). A converter uses surrounding words to guess. In a personal name, the guess can be wrong.
发 is another example: 發 (to issue, to develop) and 髮 (hair) both became 发. Phrase tables help on common words such as 头发 → 頭髮.
What this means for software
OpenCC is good on ordinary prose. It is weaker on rare names, poetry and mixed classical Chinese. That is a limit of dictionaries, not a reason to convert by hand one glyph at a time.
What you should do
Convert with the matching regional type, then search the output for 后, 发, 面, 干 and other known mergers. The proofreading guide has a wider checklist.