Yes, there are many things, but in my personal experience I can mention one particular issue, which concerns some facts related to Ho Chi Minh himself. He was the leader of Vietnam but he committed many crimes, and the most serious involved the land reforms in which hundreds of thousands of people were killed. I myself knew about that and I have written about it, but that issue is taboo in Vietnam.
On May 12th, 2015. See this statement in context.