I experienced the same issue: too many hits with SPOT ALL QSOS (not in quotes), zero hits with "SPOT ALL QSOS" (in quotes).
So I opened the PDF and did the same search. Zero hits. I don't think that exact expression exists in the manual.
Next, acting on a message from Pete N4ZR, I searched for the exact expression "SPOT ALL S&P QSOS" Zero hits again. But this failed Search was different. Turns out that the Search input field is HTML-sensing, and that & is a reserved character. This is not pretty ... but you can search for a reserved character if you know to use the HTML character code for those few reserved HTML terms. Like & and < and > and ". ugh!
So, how would you enter a search for a phrase with an embedded ampersand? replace the & with & a m p ;
Not sure how to explain this in the documentation... <sigh>