In fact there is 1 line with a 404 error related to preview:
Request URL: https://myurl:9191/nextcloud/core/preview?fileId=23&x=256&y=256&a=false&v="1b01f29adaa834a5ae96b13f2aa6fb92"
Request Method: GET
Status Code: 404
Remote Address: myIP:9191
Referrer Policy: no-referrer
cache-control: no-cache, no-store, must-revalidate
content-length: 2
content-security-policy: default-src 'none';base-uri 'none';manifest-src 'self'
content-type: application/json; charset=utf-8
date: Wed, 08 Jul 2020 10:43:06 GMT
expires: Thu, 19 Nov 1981 08:52:00 GMT
feature-policy: autoplay 'none';camera 'none';fullscreen 'none';geolocation 'none';microphone 'none';payment 'none'
pragma: no-cache
server: nginx/1.18.0
status: 404
:authority: myurl:9191
:method: GET
:path: /nextcloud/core/preview?fileId=23&x=256&y=256&a=false&v="1b01f29adaa834a5ae96b13f2aa6fb92"
:scheme: https
accept: image/webp,image/apng,image/*,*/*;q=0.8
accept-encoding: gzip, deflate, br
accept-language: de-DE,de;q=0.9,en-US;q=0.8,en;q=0.7
cookie: nc_sameSiteCookielax=true; nc_sameSiteCookiestrict=true; nc_username=x; oc_sessionPassphrase=x
sec-fetch-dest: image
sec-fetch-mode: no-cors
sec-fetch-site: same-origin
user-agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/83.0.4103.116 Safari/537.36
fileId: 23
x: 256
y: 256
a: false
v:
quot;1b01f29adaa834a5ae96b13f2aa6fb92:
quot;:
Might have the same reason as this support thread i found: Error 404 for preview on file creation
Trying to generate a public share in my photo folders brings up a permission error:
Das Weiterverteilen ist nicht erlaubt/ Distribution not permitted