While looking into T192502 (which looks at empty tokens created by ICU folding), I discovered that the monolithic Greek analyzer generates some empty tokens, too, particularly for these words: εστάτο, εστερ, εστέρ, έστερ, έστέρ, εστέρα, εστέρας, εστέρες, εστέρησε, εστερία, εστερικό, εστερικού, εστερικών, εστέρο, εστέρος, εστέρων, ήσανε, ότερ, οτέρι, ότερι, οτερό, οτέρο.
As a result, searching for any of them finds the others. Some are related, but as far as I can tell, searching for εστάτο (estáto) should not return articles with Εστέρες (estéres) and Οτερό (oteró) in the title as top hits—yet that's what happens!
A straightforward solution would be to unpack the Greek analyzer and add a filter for empty tokens. These words would no longer be conflated, and exact matches would still be available through the plain index.