Nextcloud > context menu greyed out

Good evening
Nextcloud version (eg, 20.0.5): Nextcloud 25.0.2.3
Operating system and version (eg, Ubuntu 20.04):
desktop client for Windows 10 64 bit
server: Linux(CentOS, version not given in the specification)
Apache or nginx version (eg, Apache 2.4.25): Apache 2.4.x (that is what I found in the server specification)
PHP version (eg, 7.4): PHP ver8.0

$CONFIG = array (
  'instanceid' => 'sensitive data removed by Mod/JK',
  'passwordsalt' => 'sensitive data removed by Mod/JK',
  'secret' => 'sensitive data removed by Mod/JK',
  'trusted_domains' => 
  array (
    0 => 'einklang.parasite.jp',
  ),
  'datadirectory' => '/home/users/1/parasite.jp-einklang/web/nextcloud/data',
  'dbtype' => 'mysql',
  'version' => '25.0.2.3',
  'overwrite.cli.url' => 'https://einklang.parasite.jp/nextcloud',
  'dbname' => 'xxx-nextcloud',
  'dbhost' => 'mysq-xxx',
  'dbport' => '',
  'dbtableprefix' => 'oc_',
  'mysql.utf8mb4' => true,
  'dbuser' => 'xxx',
  'dbpassword' => 'xxx',
  'installed' => true,
);

I do not know how to call this particular interface item:
Right click on any folder/filer -> context menu appears -> somewhere in between in "Nextcloud >" 
If you click on that, you get another context menu:
* Activity
* Edit
* Share options
* Copy public link
* Copy internal link
* Currently available locally
* Make always available locally
* Free up local space

*** IF *** files or folders are actually synchronize and appear on other devices too, the first six items are available, but the last two items are greyed out.
When files or folders are *** NOT *** synchronized due to some incomprehensible error (I am supposed to look that up in the "Logging", but I do not understand what is written there), something that happens "at random", then the greyed out portion is reversed = first six items greyed out.

Is there any trick to fix this? If not, Nextcloud is useless, since it synchronizes files only, when it is "in the mood".
Which is not good, when you depend on the availability of certain files for  your work.
Actually, this is basically the same question as asked before:
https://help.nextcloud.com/t/file-could-not-be-synced-due-to-an-error/151890/3?u=nyuwa

No possible solutions have been offered.

I am fiddling with Nextcloud for weeks now. Today the "Administration Logging" says:
Warning   Core   Renewing session token failed

A typical log from a few days ago looks like this:
2022/12/15

[PHP] Error: Error: exif_read_data(): File not supported at /home/users/1/parasite.jp-einklang/web/nextcloud/lib/private/Metadata/Provider/ExifProvider.php#59 at <<closure>>

 0. <<closure>>
    OC\Log\ErrorHandler::onError(2, "exif_read_data(): File not supported", "/home/users/1/p ... p", 59, [OC\Files\Node\File {},[],null,null,8192])
 1. /home/users/1/parasite.jp-einklang/web/nextcloud/lib/private/Metadata/Provider/ExifProvider.php line 59
    exif_read_data(null, "ANY_TAG", true)
 2. /home/users/1/parasite.jp-einklang/web/nextcloud/lib/private/Metadata/MetadataManager.php line 68
    OC\Metadata\Provider\ExifProvider->execute(OC\Files\Node\File {})
 3. /home/users/1/parasite.jp-einklang/web/nextcloud/lib/private/Metadata/FileEventListener.php line 101
    OC\Metadata\MetadataManager->generateMetadata(OC\Files\Node\File {}, false)
 4. /home/users/1/parasite.jp-einklang/web/nextcloud/lib/private/EventDispatcher/ServiceEventListener.php line 87
    OC\Metadata\FileEventListener->handle(OCP\Files\Events\Node\NodeWrittenEvent {})
 5. /home/users/1/parasite.jp-einklang/web/nextcloud/3rdparty/symfony/event-dispatcher/EventDispatcher.php line 251
    OC\EventDispatcher\ServiceEventListener->__invoke(OCP\Files\Events\Node\NodeWrittenEvent {}, "OCP\\Files\\Eve ... t", Symfony\Componen ... {})
 6. /home/users/1/parasite.jp-einklang/web/nextcloud/3rdparty/symfony/event-dispatcher/EventDispatcher.php line 73
    Symfony\Component\EventDispatcher\EventDispatcher->callListeners([Closure {}], "OCP\\Files\\Eve ... t", OCP\Files\Events\Node\NodeWrittenEvent {})
 7. /home/users/1/parasite.jp-einklang/web/nextcloud/lib/private/EventDispatcher/EventDispatcher.php line 88
    Symfony\Component\EventDispatcher\EventDispatcher->dispatch(OCP\Files\Events\Node\NodeWrittenEvent {}, "OCP\\Files\\Eve ... t")
 8. /home/users/1/parasite.jp-einklang/web/nextcloud/lib/private/EventDispatcher/EventDispatcher.php line 100
    OC\EventDispatcher\EventDispatcher->dispatch("OCP\\Files\\Eve ... t", OCP\Files\Events\Node\NodeWrittenEvent {})
 9. /home/users/1/parasite.jp-einklang/web/nextcloud/lib/private/Files/Node/HookConnector.php line 118
    OC\EventDispatcher\EventDispatcher->dispatchTyped(OCP\Files\Events\Node\NodeWrittenEvent {})
10. /home/users/1/parasite.jp-einklang/web/nextcloud/lib/private/legacy/OC_Hook.php line 106
    OC\Files\Node\HookConnector->postWrite(["/opinion/images/rune.gif"])
11. /home/users/1/parasite.jp-einklang/web/nextcloud/apps/dav/lib/Connector/Sabre/File.php line 471
    OC_Hook::emit("OC_Filesystem", "post_write", ["/opinion/images/rune.gif"])
12. /home/users/1/parasite.jp-einklang/web/nextcloud/apps/dav/lib/Connector/Sabre/File.php line 398
    OCA\DAV\Connector\Sabre\File->emitPostHooks(false)
13. /home/users/1/parasite.jp-einklang/web/nextcloud/apps/dav/lib/Connector/Sabre/Directory.php line 151
    OCA\DAV\Connector\Sabre\File->put(null)
14. /home/users/1/parasite.jp-einklang/web/nextcloud/3rdparty/sabre/dav/lib/DAV/Server.php line 1098
    OCA\DAV\Connector\Sabre\Directory->createFile("rune.gif", null)
15. /home/users/1/parasite.jp-einklang/web/nextcloud/3rdparty/sabre/dav/lib/DAV/CorePlugin.php line 504
    Sabre\DAV\Server->createFile("files/Fliegen/opinion/images/rune.gif", null, null)
16. /home/users/1/parasite.jp-einklang/web/nextcloud/3rdparty/sabre/event/lib/WildcardEmitterTrait.php line 89
    Sabre\DAV\CorePlugin->httpPut(Sabre\HTTP\Request {}, Sabre\HTTP\Response {})
17. /home/users/1/parasite.jp-einklang/web/nextcloud/3rdparty/sabre/dav/lib/DAV/Server.php line 472
    Sabre\DAV\Server->emit("method:PUT", [Sabre\HTTP\Requ ... }])
18. /home/users/1/parasite.jp-einklang/web/nextcloud/3rdparty/sabre/dav/lib/DAV/Server.php line 253
    Sabre\DAV\Server->invokeMethod(Sabre\HTTP\Request {}, Sabre\HTTP\Response {})
19. /home/users/1/parasite.jp-einklang/web/nextcloud/3rdparty/sabre/dav/lib/DAV/Server.php line 321
    Sabre\DAV\Server->start()
20. /home/users/1/parasite.jp-einklang/web/nextcloud/apps/dav/lib/Server.php line 360
    Sabre\DAV\Server->exec()
21. /home/users/1/parasite.jp-einklang/web/nextcloud/apps/dav/appinfo/v2/remote.php line 35
    OCA\DAV\Server->exec()
22. /home/users/1/parasite.jp-einklang/web/nextcloud/remote.php line 171
    require_once("/home/users/1/p ... p")

PUT /nextcloud/remote.php/dav/files/Fliegen/opinion/images/rune.gif
from 218.44.121.253 by Fliegen at 2022-12-15T02:43:17+00:00


To me that looks like just about everything is wrong. But I do not know how to fix it.

Thank you.

crossposting…

closing it in favour for File synchronization trouble. Please help