Your formula is looking for a space in the text field. Notice that in the fields were you get a result, there is a space before the final dash and two digits.
It also looks like the final ending is not always a two digit number–sometimes it is three digits, and sometimes it is two digits and a letter. Sometimes this final number is preceded by a space and a dash, sometimes only by a dash, and sometimes the final number is smushed against the preceding word word. In order to get a robust formula field, you need to better define what you want removed from the string. Once you determine that, I recommend using a REGEX
function to get the text you want. There are several REGEX patterns that will get the result you want.
You say that it is urgent, but please recognize that this is a community forum of other Airtable users. Most of the people on this forum who answer questions (including myself) are people who volunteer their time and expertise.