The function "smb_mkstemp()" in "lib/util.c", which opens a temporary file, does not use the Samba VFS API: it direcly calls "mkstemp" or "mktemp" and "open". As a consequence, a VFS module which implements "opaque" Samba VFS calls, to provide a virtual file system, would not be able to manage "SMBctemp" messages. As far as I am concerned, I have no real need to support "SMBctemp" in my virtual file system, I just report the bug in case it would break other VFS modules.
database cleanup
Please retest against a current release and reopen if the issue still exists.