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
- Operating system and version (e.g., Ubuntu 24.04):
Debian Bookworm/ LineageOS 20
- Web server and version (e.g, Apache 2.4.25):
nginx 1.22.1
- Reverse proxy and version _(e.g. nginx 1.27.2)
nginx 1.22.1
- PHP version (e.g, 8.3):
8.2
- Is this the first time you’ve seen this error? (Yes / No):
No
- When did this problem seem to first start?
long time ago
- Installation method (e.g. AlO, NCP, Bare Metal/Archive, etc.)
tarball / Fdroid
- Are you using CloudfIare, mod_security, or similar? (Yes / No)
no
Summary of the issue you are facing:
Suddenly, out of “nowhere”, my synchronisation appears to go haywire, and my mobile tries to upload a ton of old files for no good reason.
I usually configure my mobile’s Nextcloud app (3.34 atm) to upload files to the standard folder, with date subfolders, and in case of conflict, ask everytime. I almost never use the app for anything else, very rarely (every few months or so) to download a file from the server. However, every once in a while, the app suddenly starts to frantically try to upload everything from my phone again, sometimes going back years, then clogging the upload queue and asking for what to do, because the file exists on the server already. This is a major nuisance, because I feel I’m either risking to lose the file, if eg. the file on the server got corrupted, or the phone skips uploading the file for some reason. I also once tried to set the uploads to “upload a new version”, but that didn’t do me any good, either. I’ve set it to “skip upload” for now.
It is also a major nuisance because I can’t even see why it wants to upload a file for the umpteenth time, and in the latest flurry, it didn’t show me the server version of the file, either.
I only noticed that this problem occurred shortly after I had upgraded the server software to version 31.
A related problem may be that, on my desktop, I also have synchronisation problems which pop up out of nowhere, where there’ll be sudden uploads and deletes(!) without me even touching any of the associated folders. On the desktop, I’m running the 3.11 of the app, from backports.
What is the suggested method of debugging this, and can the app please be more specific about what it means that the file exists etc.?
I support the idea of other posters who asked for “upload all of this folder” and “upload only after this cut-off date (ie, today)” buttons to get things back in sync.
Steps to replicate it (hint: details matter!):
-
Configure app for auto-upload and “ask every time” in case of conflict.
-
Wait an unspecified amount of time, may be weeks or months.
-
Observe massive flurries of uploads, with a ton of files (last time >> 100) in the “Waiting for upload” state.