samba - Nov 2017 - two issues on clients: multiple drives, no desktop shortcuts

scenario:

samba-DC (debian 9.2, Louis' packages, 4.6.7 until right now, now 4.6.11)

samba-fileserver (debian 8.9, 4.5.14 = upstream debian, conservative)

windows-10-clients ...

* GPOs in AD

one that basically runs a "net use W: \\server\data"
2nd creates an desktop shortcut to an exe within W: then

For most of the users (all in same AD-group) that works daily.

For some (right now two) I get (a) no icon/shortcut created and/or (b)
the same share connected to >20 drive letters.

gpresult /r on windows tells me that the GPOs were correctly "pulled"

Where to look for a solution?
Separate/additional GPO that deletes any other net drives ... or somehow
cleanup the user's local profile ... or ...

Maybe someone here has already seen these issues and has a pointer for me.

thanks, regards, Stefan