Thanks for the dump
Here is the relevant transaction (redacted slightly)
2019/08/12 13:43:03 DEBUG : HTTP REQUEST (req 0xc00013e100)
2019/08/12 13:43:03 DEBUG : MKCOL /remote.php/webdav/XXX/XXX/XXX/ HTTP/1.1
Host: XXX
User-Agent: rclone/v1.45
Authorization: XXXX
Accept-Encoding: gzip
2019/08/12 13:43:03 DEBUG : HTTP RESPONSE (req 0xc00013e100)
2019/08/12 13:43:03 DEBUG : HTTP/1.1 405 Method Not Allowed
Content-Length: 18
Cache-Control: no-store, no-cache, must-revalidate
Content-Type: text/plain; charset=utf-8
Date: Mon, 12 Aug 2019 11:43:03 GMT
Expires: Thu, 29 Oct 2015 16:16:00 GMT
Pragma: no-cache
Server: STACK-1.5
Strict-Transport-Security: max-age=31536000
X-Powered-By: TransIP
Method Not Allowed
I think this rclone not recognizing 405 as a valid response to MKCOL.
I'm also pretty sure we've fixed this already - can you try the latest release or if that doesn't work
the latest beta?