Имел такую же проблему со своим сайтом.
Проблема в агрессивном боте яндекса.
Вот что мне ответили разработчики IPS.
The issue with yandex is they have not been willing to slow their extremely high crawl rate for our network, which uses cloudfront, so the only way to slow it would be for the whole cloudfront IP range, in which they were not willing to do. I'm not sure of a solution to this issue they have, we have tried to work with them in the past many times though.