Hi Steven,
I checked the admin permissions for several file in folder wp-admin with my admin account. They all have the same permission. I also can read and write update-core.php with notepad. I can also create a new “update-core_save.php” file using notepad. This I did via remote control on my virtual server.
For update I am using normally
the ftp interface from the wp dashboard it worked for elder wp versions.
Regards
Johannes