Jetpack subscription emails don't use Gravatar

Hi!

The Jetpack subscription emails on my website don’t use the post author’s Gravatar, for some reason they use the following identicon: https://cache.mail.yandex.net/mail/c1e7aa58ec083fb493a8071bb4c18a27/0.gravatar.com/avatar/c4834daf65a4b5dd744989698ada65a7?s=50&d=identicon&r=G

As far as I understood from the related topics (topic 1, topic 2), Jetpack uses the avatar found at https://gravatar.com for the subscription emails that are sent out. But this is set correctly: https://gravatar.com/biggakniga
On the blog pages the author comments have the correct image: https://biggakniga.ru/about

So it’s only the email subscription body that doesn’t use the correct image.

How can I fix it?

ps. I’m using the latest version of Jetpack plugin (3.5.3).

https://www.ads-software.com/plugins/jetpack/