I am receiving numerous NM errors on startup, that I captured from /var/log for one boot on Aug 16 18:10: I ask if the preserved ".files in the home/user/ directories could be responsible for these errors?

In the captured "fail" list, NM is the main event per this thread 
(nm_device_get_device_type: assertion 'NM_IS_DEVICE (self)' failed)

The problem got more pronounced after:

    sudo add-apt-repository ppa:kubuntu-ppa/backports
    sudo apt update

This was added after plasma repeatedly dropped the window ornaments.

    sudo /var/log# grep fail *log| grep 'Aug 16 18:10'

kern.log:Aug 16 18:10:35 dad314159 kernel: [    0.173985] acpi PNP0A03:00: _OSC failed (AE_NOT_FOUND); disabling ASPM
kern.log:Aug 16 18:10:35 dad314159 kernel: [    4.392621] wl: module verification failed: signature and/or required key missing - tainting kernel
kern.log:Aug 16 18:10:36 dad314159 NetworkManager[997]: nm_device_get_device_type: assertion 'NM_IS_DEVICE (self)' failed
kern.log:Aug 16 18:10:36 dad314159 NetworkManager[997]: <warn>  [1502921436.6054] failed to enumerate oFono devices: GDBus.Error:org.freedesktop.DBus.Error.ServiceUnknown: The name org.ofono was not provided by any .service files
kern.log:Aug 16 18:10:43 dad314159 NetworkManager[997]: <info>  [1502921443.7380] device (wlp12s0): state change: need-auth -> failed (reason 'no-secrets') [60 120 7]
kern.log:Aug 16 18:10:43 dad314159 NetworkManager[997]: <warn>  [1502921443.7388] device (wlp12s0): Activation: failed for connection 'Disco'
kern.log:Aug 16 18:10:43 dad314159 NetworkManager[997]: <info>  [1502921443.7426] device (wlp12s0): state change: failed -> disconnected (reason 'none') [120 30 0]
syslog:Aug 16 18:10:35 dad314159 kernel: [    0.173985] acpi PNP0A03:00: _OSC failed (AE_NOT_FOUND); disabling ASPM
syslog:Aug 16 18:10:35 dad314159 kernel: [    4.392621] wl: module verification failed: signature and/or required key missing - tainting kernel
syslog:Aug 16 18:10:35 dad314159 avahi-daemon[988]: chroot.c: open() failed: No such file or directory
syslog:Aug 16 18:10:35 dad314159 thermald[961]: THD engine start failed
syslog:Aug 16 18:10:36 dad314159 NetworkManager[997]: nm_device_get_device_type: assertion 'NM_IS_DEVICE (self)' failed
syslog:Aug 16 18:10:36 dad314159 wpa_supplicant[1334]: dbus: wpa_dbus_get_object_properties: failed to get object properties: (none) none
syslog:Aug 16 18:10:36 dad314159 NetworkManager[997]: <warn>  [1502921436.6054] failed to enumerate oFono devices: GDBus.Error:org.freedesktop.DBus.Error.ServiceUnknown: The name org.ofono was not provided by any .service files
syslog:Aug 16 18:10:36 dad314159 systemd[1]: networking.service: Unit entered failed state.
syslog:Aug 16 18:10:36 dad314159 systemd[1]: ctdb.service: Unit entered failed state.
syslog:Aug 16 18:10:36 dad314159 colord[1188]: (colord:1188): Cd-WARNING **: failed to get session [pid 1021]: No such device or address
syslog:Aug 16 18:10:39 dad314159 systemd[1]: sddm.service: Unit entered failed state.
syslog:Aug 16 18:10:41 dad314159 colord[1188]: (colord:1188): Cd-WARNING **: failed to get session [pid 1494]: No such device or address
syslog:Aug 16 18:10:42 dad314159 systemd[1]: sddm.service: Unit entered failed state.
syslog:Aug 16 18:10:43 dad314159 NetworkManager[997]: <info>  [1502921443.7380] device (wlp12s0): state change: need-auth -> failed (reason 'no-secrets') [60 120 7]
syslog:Aug 16 18:10:43 dad314159 NetworkManager[997]: <warn>  [1502921443.7388] device (wlp12s0): Activation: failed for connection 'Disco'
syslog:Aug 16 18:10:43 dad314159 NetworkManager[997]: <info>  [1502921443.7426] device (wlp12s0): state change: failed -> disconnected (reason 'none') [120 30 0]

I had made the unfortunate "upgrade" from kubuntu 14.04 with kxstudio and decided to do a clean install to clean up the previous mess, leaving kxstudio out (because kxstudio is skipping 16.04 in favor of 18.04):

I re-installed kubuntu 16.04,3 from disk downloaded 5 days ago (1.562.112KB) preserving the /home/dad partition as well as a copy of the fstab: (shows what was preserved during install on /dev/sd8

     sudo /etc# cat fstab

# /etc/fstab: static file system information.
#
# Use 'blkid' to print the universally unique identifier for a
# device; this may be used with UUID= as a more robust way to name devices
# that works even if disks are added and removed. See fstab(5).
#
# <file system> <mount point>   <type>  <options>       <dump>  <pass>
# / was on /dev/sda8 during installation
UUID=27aec088-dbbf-44f9-9c61-ab3c933e054e /               ext3    errors=remount-ro 0       1

# /home was on /dev/sda6 during installation
UUID=cfb5d746-bb65-4061-ba5b-02f60d574c27 /home           ext4    defaults        0       2

# swap was on /dev/sda5 during installation
UUID=540c3467-7148-463e-858a-cb1435e4503f none            swap    sw              0       0

# mount Windows-Linux Share or /dev/sda3 on /media/sda3  
UUID=62587745587716CF                    /media/sda3  ntfs  nls=iso8859-1,rw,umask=000  0  0

# mount usb as execuitable at /media/usb
# /dev/sde1 /media/usb vfat umask=0222,rw,users,exec 0 

# Data segment 69 gig
UUID=1539c626-fcb7-42ff-a0df-15494d9e1c40 /media/Data ext4 errors=remount-ro             0  2