You are right, normally you could see the correct data even with a 5% error. However I had a similar experience using one of those modules which probably had a counterfeit FT232RL IC. Yes, the baud rate error could be caused from a clock missconfigur...

Most probably you already have found the answer since almost a year has passed from your last post..Anyway this is because of wrong Baud Rate. By checking the USART1 initilization function I've notice that there is a typo on "huart1.Init.BaudRate = ...