Limesurvey can't write to uploads folder

[alain0]

Describe the bug

Limesurvey can't write to the uploads folder. When I, for instance, try to upload an image within the theme options of a survey I get the error "Incorrect permissions in your /home/yunohost.app/limesurvey/upload/surveys/352969/images/ folder."
I have checked and ownership of the upload folder (/home/yunohost.app/limesurvey/upload) and its subfolders are set to limesurvey:www-data with write right for both user and group (rwxrwxr-x).

Context

• Hardware: tested on two installs, Hetzner VPS and old laptop at home
• YunoHost version: 11.2.14.1
• I have access to my server: Through SSH | through the webadmin
• Are you in a special context or did you perform some particular tweaking on your YunoHost instance?: no
• Using, or trying to install package version/branch: 6.5.11~ynh1

Steps to reproduce

• On a fresh install:
  1. Create a survey
  2. Go to "Theme options" within the settings of this survey
  3. Click "Customize theme"
  4. Go to the "Images" tab and upload an image
  5. See error at the top (dissappears quickly)

Expected behavior

Image files are written to /home/yunohost.app/limesurvey/upload

Logs

The error is not logged in the nginx logs