Document does not contain text

In Yandex Webmaster, site pages quite often fly out of the search due to the error “The document does not contain text.” I contacted Yandex support and received the answer:

We checked that from time to time when the robot accesses the pages of your site, the server returns documents with a size of 0 bytes, so they cannot be indexed and are excluded from the search. If this situation arises, please contact the administrator of the site or server on which it is located. For example, an error occurred when accessing the page https://huaweihelp.ru/obzor-honor-magicwatch-2-nedelya-s-umnymi-chasami/ 2021-04-12 at 06:27:04 UTC.

When the pages become available, they will be able to return to the search as the robot crawls the site with subsequent updates to the search base.

Then I contacted hosting support:

Yes, we see this request:

5.255.253.91 - - [12 / Apr / 2021: 09: 27: 04 +0300] huaweihelp.ru GET / obzor-honor-magicwatch-2-nedelya-s-umnymi-chasami / HTTP / 1.1 200 0 "-" " Mozilla / 5.0 (compatible; YandexBot / 3.0; + http: //yandex.com/bots) "" - "0.510-0.510

The site scripts actually generated an empty response to it. We checked the error logs at this moment, no entries were found. Judging by the fact that an empty response was returned with a response code of 200, the site scripts generated the page without errors, but for some unknown reason did not contain data.

In this case, we recommend checking the parameters of the caching extension, perhaps there is a problem with it, try clearing the CMS cache, for more information, we recommend that you contact the specialized specialists in the development of sites on CMS WordPress.

Can you please tell me what could be the problem?

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