From your experience what are the most common reasons that causes log shipping failures?

[Bentley]

Hi everyone, I'd like to ask you a question, I'd like to know from your experience what are the most common reasons that causes log shipping failures? Thank you for your answer as soon as possible.

[Jeremiah]

Error #1: Exclusive access could not be obtained because the database is in use.
Error #2: The log in this backup set begins at LSN <#>, which is too recent to apply to the database
Error #3: Directory lookup for the file <location> failed with the operating system error 2(The system cannot find the file specified.)