Using verb-lemma:μακάριος does not find all instances of the lemma μακάριος in the LSGNT. A sample is shown below. A lemma search using the normal Bible Search tool finds all of them.

Above you can see only three of the nine times the verb μακάριος appears in Matthew 5:1-11 appear.
Unless I misunderstand something it appears to be a bug in the search engine.