I will not walk through your code and point out to you what and where, but give you an example.

Let us say that a thorough examination of the code show there is 18 possibilities for the code to hang on a bad transmission event.

the incompetent person will find and fix one and when the thing do not work find and fix another ... till the thing 'works' then say "happy me"

the competent person will fix all 18 and when all 18 are fixed and the thing works say "let me check the code again"

the proper way to test code like yours is to set a high baudrate and find that the thing still works without hitches, but slower because of the many retries.

Erik