Support intro
Sorry to hear you’re facing problems. 
The community help forum (help.nextcloud.com) is for home and non-enterprise users. Support is provided by other community members on a best effort / “as available” basis. All of those responding are volunteering their time to help you.
If you’re using Nextcloud in a business/critical setting, paid and SLA-based support services can be accessed via portal.nextcloud.com where Nextcloud engineers can help ensure your business keeps running smoothly.
Getting help
In order to help you as efficiently (and quickly!) as possible, please fill in as much of the below requested information as you can.
Before clicking submit: Please check if your query is already addressed via the following resources:
- Official documentation (searchable and regularly updated)
- How to topics and FAQs
- Forum search
(Utilizing these existing resources is typically faster. It also helps reduce the load on our generous volunteers while elevating the signal to noise ratio of the forums otherwise arising from the same queries being posted repeatedly).
Some or all of the below information will be requested if it isn’t supplied; for fastest response please provide as much as you can. 
The Basics
- Nextcloud Server version (e.g., 29.x.x):
31.0.8
- Operating system and version (e.g., Ubuntu 24.04):
TrueNAS25.04.2.4
- Web server and version (e.g, Apache 2.4.25):
AIO
- Reverse proxy and version _(e.g. nginx 1.27.2)
AIO
- PHP version (e.g, 8.3):
AIO
- Is this the first time you’ve seen this error? (Yes / No):
No
- When did this problem seem to first start?
Always with that calendar
- Installation method (e.g. AlO, NCP, Bare Metal/Archive, etc.)
AIO
- Are you using CloudfIare, mod_security, or similar? (Yes / No)
No
Summary of the issue you are facing:
I use NC calendar app with several different calendars (4). One of these 4 calendars is loading quite slowly (takes about 5-10 seconds to load). If you actually using the calendar, these 5-10 seconds are triggered at each small step that you might take, for example switching between one week and the next week always triggers the delay, creating an appointment triggers the delay, etc.
If I hide this one calendar, everything is very fast and responsive.
The specific calendar is my work/office calendar, which is synced with caldavsync between my PC from work/office (which uses Outlook) and my NC instance (which holds all my appointments, private and work).
This work calendar holds all my work appointment from years back. Nothing fancy or extreme, to my mind.
Steps to replicate it (hint: details matter!):
- Load the calendar-view (I typically use week-view) with the specific calendar selected.
- Problem disappears, if the specific calendar is hidden.
Troubleshooting
I tried troubleshooting the issue with Chat-GPT. It wanted to have network-trace, which didn’t show anything telling. Then it wanted to have an export of the problematic calendar. If I try this, NC throws a fatal error that
–> Request used more than 300 MB of RAM: 479.7 MB”
–> Allowed memory size of 536870912 bytes exhausted (tried to allocate 28686776 bytes) at /var/www/html/3rdparty/sabre/http/lib/Sapi.php#80
GET /remote.php/dav/calendars/airflow/outlook-1/?export
from 192.168.0.45 by airflow at 17.09.2025, 18:54:15
the full raw entries are below!
Log entries
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":"ndTuJr5ckqHVJc4OZvNX","level":3,"time":"2025-09-17T17:07:59+00:00","remoteAddr":"192.168.0.45","user":"--","app":"no app in context","method":"GET","url":"/apps/logreader/api/poll?lastReqId=h9IWiSSVh1S84gGAce2q","message":"Slow session operation session_start detected","userAgent":"Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/138.0.0.0 Safari/537.36","version":"31.0.8.1","data":{"parameters":"[{\"cookie_samesite\":\"Lax\"}]","timeSpent":"35.699723958969116"},"id":"68caeb3330b24"}
{"reqId":"v6HvUr6mhvzwsnVtmBXN","level":2,"time":"2025-09-17T17:07:52+00:00","remoteAddr":"192.168.0.45","user":"--","app":"no app in context","method":"PROPFIND","url":"/remote.php/dav/calendars/airflow/","message":"Slow session operation session_start detected","userAgent":"Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/138.0.0.0 Safari/537.36","version":"31.0.8.1","data":{"parameters":"[{\"cookie_samesite\":\"Lax\"}]","timeSpent":"22.60184407234192"},"id":"68caeb3e2f237"}
{"reqId":"h9IWiSSVh1S84gGAce2q","level":4,"time":"2025-09-17T16:54:15+00:00","remoteAddr":"192.168.0.45","user":"airflow","app":"core","method":"GET","url":"/remote.php/dav/calendars/airflow/outlook-1/?export","message":"Request used more than 300 MB of RAM: 479.7 MB","userAgent":"Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/138.0.0.0 Safari/537.36","version":"31.0.8.1","data":{"app":"core"},"id":"68caeb3e2f243"}
{"reqId":"h9IWiSSVh1S84gGAce2q","level":3,"time":"2025-09-17T16:54:15+00:00","remoteAddr":"192.168.0.45","user":"airflow","app":"PHP","method":"GET","url":"/remote.php/dav/calendars/airflow/outlook-1/?export","message":"Allowed memory size of 536870912 bytes exhausted (tried to allocate 28686776 bytes) at /var/www/html/3rdparty/sabre/http/lib/Sapi.php#80","userAgent":"Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/138.0.0.0 Safari/537.36","version":"31.0.8.1","data":{"app":"PHP"},"id":"68caeb3e2f24b"}
