epubviewer causes iOS and MacOS clients to fail to sync card and cal DAV 
I am experiencing a problem with the epubviewer APP version 1.7.2. When I activate the app on my Nextcloud 31.0.0.18, I receive an extremely large number of PHP error messages.
There are so many error messages that the calDAV and cardDAV sync no longer works and is aborted with an Error 500… When I deactivate the app, the error messages stop and the calendar sync starts working again.
additionally I get this error if the epubviewer app is active:
- Dein Webserver ist noch nicht hinreichend für Datei-Synchronisierung konfiguriert, da die WebDAV-Schnittstelle vermutlich nicht funktioniert. Damit diese Prüfung ausgeführt werden kann, musst du sicherstellen, dass dein Webserver eine Verbindung zu sich selbst herstellen kann. Daher muss er in der Lage sein, mindestens eine seiner trusted_domains oder ‘overwrite.cli.url’ aufzulösen und eine Verbindung zu ihnen herzustellen. Dieser Fehler kann das Ergebnis einer serverseitigen DNS-Nichtübereinstimmung oder einer ausgehenden Firewall-Regel sein.
if I deactivate the app - this error message also disappears.
The Basics
- Nextcloud Server version (e.g., 29.x.x):
- 31.0.0.18
- Operating system and version (e.g., Ubuntu 24.04):
- Linux Red Hat 4.18.0-553.34.1
- Web server and version (e.g, Apache 2.4.25):
- Apache/2.4.37
- PHP version (e.g, 8.3):
- Version: 8.3.17
- Is this the first time you’ve seen this error? (Yes / No):
- yes
- When did this problem seem to first start?
- upgrade to NC 31
- Installation method (e.g. AlO, NCP, Bare Metal/Archive, etc.)
- cli upgrade
- Are you using CloudfIare, mod_security, or similar? (Yes / No)
- no
Summary of the issue you are facing:
mobile clients get Error 500 if trying to connect to card or calDAV on iCal
https interface works fine
client webdav sync works fine
Steps to replicate it (hint: details matter!):
- activate epubviewer
- → sync is broken
- deactivate epubviewer
- → sync works again
Log entries
Declaration of Psr\Log\AbstractLogger::emergency(Stringable| string Smessage, array Scontext = l]) must be compatible with Psr\Log\LoggerInterface::emergency(Stringable| string Smessage, array $context = []): void at /nextcloud/apps/epubviewer/vendor/ psr/log/src/LoggerTrait.php#23
Nextcloud
Please provide the log entries from your Nextcloud log that are generated during the time of problem (via the Copy raw option from Administration settings->Logging screen or from your nextcloud.log located in your data directory). Feel free to use a pastebin/gist service if necessary.
{"reqId":"Z8AHggq6Lhn0N9YWLdyrEQAAAVk","level":3,"time":"2025-02-27T06:34:42+00:00","remoteAddr":"xxx:xxx:xxx:xxx::xxx","user":false,"app":"PHP","method":"PROPFIND","url":"/remote.php/webdav","message":"Declaration of Psr\\Log\\AbstractLogger::emergency(Stringable|string $message, array $context = []) must be compatible with Psr\\Log\\LoggerInterface::emergency(Stringable|string $message, array $context = []): void at /xxx/xxx/nextcloud.xxx.de/apps/epubviewer/vendor/psr/log/src/LoggerTrait.php#23","userAgent":"Nextcloud Server Crawler","version":"31.0.0.18","data":{"app":"PHP"}}
repeat for the next 40+ MB
Web Browser
NONE
Web server / Reverse Proxy
The output of your Apache/nginx/system log in /var/log/____:
NONE
