File upload via owncloud webinterface works. 
File upload via rclone webdav failed. 
So i think its a bug. Support said there is no upload limit.
Ok here is the command (copy single file):
rclone copy Movies/MyMovie/************-1080p.mkv owncube:/movies/ --dump headers
Log:
2023/10/04 09:47:50 NOTICE: Automatically setting -vv as --dump is enabled
2023/10/04 09:47:50 DEBUG : rclone: Version "v1.63.0" starting with parameters ["rclone" "copy" "Movies/MyMovie/************-1080p.mkv" "owncube:/movies/" "--dump" "headers"]
2023/10/04 09:47:50 DEBUG : Creating backend with remote "Movies/MyMovie/************-1080p.mkv"
2023/10/04 09:47:50 DEBUG : Using config file from "/home/dev/.config/rclone/rclone.conf"
2023/10/04 09:47:50 DEBUG : fs cache: adding new entry for parent of "Movies/MyMovie/************-1080p.mkv", "/home/dev/Downloads/Movies/Tenet.2020.German.DTS.DL.1080p.BluRay.x264-COiNCiDENCE"
2023/10/04 09:47:50 DEBUG : Creating backend with remote "owncube:/movies/"
2023/10/04 09:47:50 DEBUG : found headers:
2023/10/04 09:47:50 DEBUG : You have specified to dump information. Please be noted that the Accept-Encoding as shown may not be correct in the request and the response may not show Content-Encoding if the go standard libraries auto gzip encoding was in effect. In this case the body of the request will be gunzipped before showing it.
2023/10/04 09:47:50 DEBUG : fs cache: renaming cache item "owncube:/movies/" to be canonical "owncube:movies"
2023/10/04 09:47:50 DEBUG : >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
2023/10/04 09:47:50 DEBUG : HTTP REQUEST (req 0xc00041a500)
2023/10/04 09:47:50 DEBUG : PROPFIND /remote.php/dav/files/mydomain/movies/************-1080p.mkv HTTP/1.1
Host: owncube.cloud
User-Agent: rclone/v1.63.0
Content-Length: 287
Authorization: XXXX
Depth: 1
Referer: https://owncube.cloud/remote.php/dav/files/mydomain/
Accept-Encoding: gzip
2023/10/04 09:47:50 DEBUG : >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
2023/10/04 09:47:55 DEBUG : <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
2023/10/04 09:47:55 DEBUG : HTTP RESPONSE (req 0xc00041a500)
2023/10/04 09:47:55 DEBUG : HTTP/1.1 404 Not Found
Cache-Control: no-store, no-cache, must-revalidate
Connection: Upgrade
Content-Security-Policy: default-src 'none';
Content-Type: application/xml; charset=utf-8
Date: Wed, 04 Oct 2023 07:47:51 GMT
Dav: 1, 3, extended-mkcol, access-control, calendarserver-principal-property-search, nextcloud-checksum-update, nc-calendar-search, nc-enable-birthday-calendar
Expires: Thu, 19 Nov 1981 08:52:00 GMT
Pragma: no-cache
Referrer-Policy: no-referrer
Server: Apache
Set-Cookie: ocs0qrwccts3=69234578c343d2da414f64ff013f0fe5; path=/; secure; HttpOnly; SameSite=Lax
Set-Cookie: oc_sessionPassphrase=OmShqOGl8rdjliJfcwm8bEVbKfLN9MyPjXVkrZhjwUAg1AScmzj9Pe2uyOZyuszUDOr6HwSRQJmGKsQ0v7ReKwCwpIxBS7k2ZEqVQ%2FzsdMEUKgiBsAp9dsZwYvLRrhdx; path=/; secure; HttpOnly; SameSite=Lax
Set-Cookie: ocs0qrwccts3=b304198f3488d7eece96c3c68314400d; path=/; secure; HttpOnly; SameSite=Lax
Set-Cookie: ocs0qrwccts3=b304198f3488d7eece96c3c68314400d; path=/; secure; HttpOnly; SameSite=Lax
Set-Cookie: __Host-nc_sameSiteCookielax=true; path=/; httponly;secure; expires=Fri, 31-Dec-2100 23:59:59 GMT; SameSite=lax
Set-Cookie: __Host-nc_sameSiteCookiestrict=true; path=/; httponly;secure; expires=Fri, 31-Dec-2100 23:59:59 GMT; SameSite=strict
Set-Cookie: ocs0qrwccts3=b304198f3488d7eece96c3c68314400d; path=/; secure; HttpOnly; SameSite=Lax
Set-Cookie: ocs0qrwccts3=b304198f3488d7eece96c3c68314400d; path=/; secure; HttpOnly; SameSite=Lax
Set-Cookie: ocs0qrwccts3=6e73be0e7364810ca112fda538bddd90; path=/; secure; HttpOnly; SameSite=Lax
Set-Cookie: cookie_test=test; expires=Wed, 04 Oct 2023 08:47:54 GMT; Max-Age=3600
Strict-Transport-Security: max-age=31536000; preload
Upgrade: h2
Vary: Brief,Prefer,Accept-Encoding
X-Content-Type-Options: nosniff
X-Content-Type-Options: nosniff
X-Frame-Options: SAMEORIGIN
X-Frame-Options: SAMEORIGIN
X-Permitted-Cross-Domain-Policies: none
X-Robots-Tag: noindex, nofollow
X-Xss-Protection: 1; mode=block
2023/10/04 09:47:55 DEBUG : <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
2023/10/04 09:47:55 DEBUG : ***************-1080p.mkv: Need to transfer - File not found at Destination
2023/10/04 09:47:55 DEBUG : >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
2023/10/04 09:47:55 DEBUG : HTTP REQUEST (req 0xc00041b300)
2023/10/04 09:47:55 DEBUG : MKCOL /remote.php/dav/files/mydomain/movies/ HTTP/1.1
Host: owncube.cloud
User-Agent: rclone/v1.63.0
Authorization: XXXX
Referer: https://owncube.cloud/remote.php/dav/files/mydomain/
Accept-Encoding: gzip
2023/10/04 09:47:55 DEBUG : >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
2023/10/04 09:47:59 DEBUG : <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
2023/10/04 09:47:59 DEBUG : HTTP RESPONSE (req 0xc00041b300)
2023/10/04 09:47:59 DEBUG : HTTP/1.1 405 Method Not Allowed
Allow: OPTIONS, GET, HEAD, DELETE, PROPFIND, PUT, PROPPATCH, COPY, MOVE, REPORT
Cache-Control: no-store, no-cache, must-revalidate
Content-Security-Policy: default-src 'none';
Content-Type: application/xml; charset=utf-8
Date: Wed, 04 Oct 2023 07:47:55 GMT
Expires: Thu, 19 Nov 1981 08:52:00 GMT
Pragma: no-cache
Referrer-Policy: no-referrer
Server: Apache
Set-Cookie: ocs0qrwccts3=744c3b27b63ada12187b63071623aea7; path=/; secure; HttpOnly; SameSite=Lax
Set-Cookie: oc_sessionPassphrase=imWGOofU5L%2Fe3K4x0y0cP3JLJpQtFGD5ogkdZmRI376keW4HPojahW%2Fc2xpqpXrhQzUBvbQVTrsk%2BaRo0qAsvigePtKLAZWLoVedv%2F0oIq2XhwmjbbP2YYr%2BKUMgKhRa; path=/; secure; HttpOnly; SameSite=Lax
Set-Cookie: ocs0qrwccts3=bc28d66d0ddc9095bdfa7bf382e1fa59; path=/; secure; HttpOnly; SameSite=Lax
Set-Cookie: ocs0qrwccts3=bc28d66d0ddc9095bdfa7bf382e1fa59; path=/; secure; HttpOnly; SameSite=Lax
Set-Cookie: __Host-nc_sameSiteCookielax=true; path=/; httponly;secure; expires=Fri, 31-Dec-2100 23:59:59 GMT; SameSite=lax
Set-Cookie: __Host-nc_sameSiteCookiestrict=true; path=/; httponly;secure; expires=Fri, 31-Dec-2100 23:59:59 GMT; SameSite=strict
Set-Cookie: ocs0qrwccts3=bc28d66d0ddc9095bdfa7bf382e1fa59; path=/; secure; HttpOnly; SameSite=Lax
Set-Cookie: ocs0qrwccts3=bc28d66d0ddc9095bdfa7bf382e1fa59; path=/; secure; HttpOnly; SameSite=Lax
Set-Cookie: ocs0qrwccts3=5cc6f311f44ae54a391d5a9aab9106e8; path=/; secure; HttpOnly; SameSite=Lax
Set-Cookie: cookie_test=test; expires=Wed, 04 Oct 2023 08:47:59 GMT; Max-Age=3600
Strict-Transport-Security: max-age=31536000; preload
Vary: Accept-Encoding
X-Content-Type-Options: nosniff
X-Content-Type-Options: nosniff
X-Frame-Options: SAMEORIGIN
X-Frame-Options: SAMEORIGIN
X-Permitted-Cross-Domain-Policies: none
X-Robots-Tag: noindex, nofollow
X-Xss-Protection: 1; mode=block
2023/10/04 09:47:59 DEBUG : <<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<
2023/10/04 09:47:59 DEBUG : **************-1080p.mkv: Update will use the normal upload strategy (no chunks)
2023/10/04 09:48:50 INFO :
Transferred: 0 B / 7.841 GiB, 0%, 0 B/s, ETA -
Transferred: 0 / 1, 0%
Elapsed time: 1m0.1s
Transferring:
* ******************-1080p.mkv: 0% /7.841Gi, 0/s, -
2023/10/04 09:49:51 INFO :
Transferred: 0 B / 7.841 GiB, 0%, 0 B/s, ETA -
Transferred: 0 / 1, 0%
Elapsed time: 2m0.4s
Transferring:
* ******************-1080p.mkv: 0% /7.841Gi, 0/s, -
Killed