Multi-select fields containing a value with a " (double quote) in it yield unexpected results with formulas—essentially because Airtable seems to escape double quotes in arrays with another double quote rather than a backslash or something else.
Here’s a series of formula results on a multi-select field named {multi} containing a single option with the value: 6" Bar Pull
Formula: {multi}
Result: “6"” Bar Pull"
Formula: FIND('6" Bar Pull",{multi})
Result: 0
Formula: FIND(‘6" Bar Pull’, REPLACE(multi, FIND(’""’, multi), 2, ‘"’))
Result: 2