The calculation syntax looks correct. It would appear that one of the three comparisons are not True due to a value that doesn't exactly match. This could be something very hard to spot such as an extra space or return character in a text field. It might also be a relationship issue where your record with the fields Vessel_#_1, etc is not matching to the expected record in Vessel Schedule.
You'll need to do some very careful checking.
And if this is a calculation field, you'll need to also consider what is selected in the "context" drop down at the top of the specify calculation dialog as this can make a difference in the results returned.