Upload problem for files >1MB via the web interface (expected file size ... got ...)

I did the following search here:

https://central.owncloud.org/search?q=expected%20filesize
https://doc.owncloud.org/server/latest/admin_manual/search.html?q=expected+filesize

and stumbled over the following resources which could help:

https://doc.owncloud.org/server/latest/admin_manual/issues/general_troubleshooting.html?highlight=expected%20filesize#common-problems-error-messages