Also depending on what you're doing in your code, there were even some changes in 4.53 (one of the best releases IMHO) over 4.51 that could have broken your script.

If you want you can post your script (removing any personal data) here and I'm sure we can help you to locate what the issue might be.

Search the board for the SANITY UDF as well which can help to find and correct easy mistakes in structure.