Well you system log doesn’t show a connectivity loss at 19:37 which might indiciate that it is not a low level network disconnect but a Kodi issue. But you also seems to have copied stuff wrongly in your smb.conf.
Can you share your smb.conf and user.conf?
Sep 11 19:35:46 osmc mediacenter[328]: Unknown parameter encountered: "//client lanman auth"
Sep 11 19:35:46 osmc mediacenter[328]: Ignoring unknown parameter "//client lanman auth"
Sep 11 19:35:46 osmc mediacenter[328]: Unknown parameter encountered: "//lanman auth"
Sep 11 19:35:46 osmc mediacenter[328]: Ignoring unknown parameter "//lanman auth"
Sep 11 19:35:46 osmc mediacenter[328]: Unknown parameter encountered: "//client lanman auth"
Sep 11 19:35:46 osmc mediacenter[328]: Ignoring unknown parameter "//client lanman auth"
Sep 11 19:35:46 osmc mediacenter[328]: Unknown parameter encountered: "//lanman auth"
Sep 11 19:35:46 osmc mediacenter[328]: Ignoring unknown parameter "//lanman auth"
Would you consider to use fstab based mount for testing if that allows stable playing?