It "finds" lots of examples where the found text doesn't match the search for text - see screenshot as an example. It also misses actual occurrences of the search text - in the screenshot, "Article 50" exists much earlier in the document. You can see it also thinks there are over 7,000 instances of the search term in the doc - there are actually fewer than 100.
To fix this I usually end up having to close and reopen the doc. It's an intermittent fault.
I run Windows 11 on a PC.