TYPO3 Core

I have set up meta tags on a website. At some point they will disappear as their cache-entry somehow is empty. I have no idea why this keeps happening. This problem appears seemingly at random after some time. Clearing the cache in the backend resolves the problem.

I have set up some debugging in \TYPO3\CMS\Core\Page\PageRenderer in the renderMetaTagsFromAPI method.

[...]

----------

[date]: renderMetaTagsFromAPI
cacheIdentifier = randomhash465zui-metatag-edge
render new
no properties
---
cacheIdentifier = randomhash465zui-metatag-html5
render from cache
do not set cache:
Array
(
    [cache] => TYPO3\CMS\Core\Cache\Frontend\VariableFrontend
    [existingCacheEntry] => 1
    [page] => 1
)
properties:
<meta name="generator" content="TYPO3 CMS" />
<meta name="description" content="My Website" />
<meta name="author" content="Author" />
<meta name="keywords" content="My Website" />
---
cacheIdentifier = randomhash465zui-metatag-httpsOpenGraph
render from cache
do not set cache:
Array
(
    [cache] => TYPO3\CMS\Core\Cache\Frontend\VariableFrontend
    [existingCacheEntry] => 1
    [page] => 1
)
properties:
<meta property="og:image:secure_url" content="https://www.mywebsite.com/my-image.jpg" />
---
cacheIdentifier = randomhash465zui-metatag-opengraph
render from cache
do not set cache:
Array
(
    [cache] => TYPO3\CMS\Core\Cache\Frontend\VariableFrontend
    [existingCacheEntry] => 1
    [page] => 1
)
properties:
<meta property="og:title" content="Title" />
<meta property="og:description" content="Description" />
<meta property="og:image" content="https://www.mywebsite.com/my-image.jpg" />
<meta property="og:image:url" content="https://www.mywebsite.com/my-image.jpg" />
<meta property="og:image:width" content="123" />
<meta property="og:image:height" content="123" />
---
cacheIdentifier = randomhash465zui-metatag-twitter
render new
no properties
---
cacheIdentifier = randomhash465zui-metatag-generic
render from cache
do not set cache:
Array
(
    [cache] => TYPO3\CMS\Core\Cache\Frontend\VariableFrontend
    [existingCacheEntry] => 1
    [page] => 1
)
properties:
<meta name="language" content="de" />
---
metaTags:
Array
(
    [0] => <meta name="generator" content="TYPO3 CMS" />
<meta name="description" content="My Website" />
<meta name="author" content="Author" />
<meta name="keywords" content="My Website" />
    [1] => <meta property="og:image:secure_url" content="https://www.mywebsite.com/my-image.jpg" />
    [2] => <meta property="og:title" content="Title" />
<meta property="og:description" content="Description" />
<meta property="og:image" content="https://www.mywebsite.com/my-image.jpg" />
<meta property="og:image:url" content="https://www.mywebsite.com/my-image.jpg" />
<meta property="og:image:width" content="123" />
<meta property="og:image:height" content="123" />
    [3] => <meta name="language" content="abc" />
)

----------

[same date as entry above + a few minutes]: renderMetaTagsFromAPI
cacheIdentifier = randomhash123qwe-metatag-edge
render new
no properties
---
cacheIdentifier = randomhash123qwe-metatag-html5
render from cache
do not set cache:
Array
(
    [cache] => TYPO3\CMS\Core\Cache\Frontend\VariableFrontend
    [existingCacheEntry] => 1
    [page] => 1
)
properties:
<meta name="generator" content="TYPO3 CMS" />
---
cacheIdentifier = randomhash123qwe-metatag-httpsOpenGraph
render new
no properties
---
cacheIdentifier = randomhash123qwe-metatag-opengraph
render new
no properties
---
cacheIdentifier = randomhash123qwe-metatag-twitter
render new
no properties
---
cacheIdentifier = randomhash123qwe-metatag-generic
render new
no properties
---
metaTags:
Array
(
    [0] => <meta name="generator" content="TYPO3 CMS" />
)

----------

[...]

As you can see, the meta tags are missing in the second debug entry, just a few moments after the debug entry above.

Has someone encountered this error as well? Seems to me, that cacheing is somehow broken.