I have reproduced this issue a few times on my LXQt system.
systemctl isolate multi-user-target
closes most user processes, but fails to close lxqt-panel.
After running full-upgrade or whatever in the console session you issue
systemctl isolate graphical-target && exit
The LXQt desktop fails to start correctly.
If, however, while in the console session you kill -9 the user process for lxqt-panel, then you can restart the LXQt desktop with systemctl isolate graphical.target && exit
Here is my system:
System: Host: n5110 Kernel: 4.14.9-towo.1-siduction-amd64 x86_64 bits: 64
Desktop: LXQt
Distro: siduction 17.1.0 Patience - lxqt - (201703051830)
Machine: Device: portable System: Dell product: Inspiron N5110 serial: N/A
Mobo: Dell model: 034W60 v: A11 serial: N/A
BIOS: Dell v: A11 date: 08/03/2012
CPU: Dual core Intel Core i3-2330M (-HT-MCP-) cache: 3072 KB
clock speeds: max: 2200 MHz 1: 900 MHz 2: 1100 MHz 3: 2200 MHz
4: 900 MHz
Graphics: Card: Intel 2nd Generation Core Integrated Graphics Controller
Display Server: x11 (X.Org 1.19.5 )
drivers: modesetting (unloaded: fbdev,vesa)
Resolution: 1366x768@60.00hz
OpenGL: renderer: Mesa DRI Intel Sandybridge Mobile
version: 3.3 Mesa 17.3.1
Audio: Card Intel 6 Series/C200 Series Family High Def. Audio Controller
driver: snd_hda_intel
Sound: ALSA v: k4.14.9-towo.1-siduction-amd64
Network: Card-1: Realtek RTL8101/2/6E PCIE Fast/Gigabit Ethernet controller
driver: r8169
IF: enp5s0 state: down mac: <filter>
Card-2: Intel Centrino Wireless-N 1030 [Rainbow Peak]
driver: iwlwifi
IF: wlp9s0 state: up mac: <filter>
Drives: HDD Total Size: 80.0GB (14.0% used)
ID-1: /dev/sda model: INTEL_SSDSA2CW08 size: 80.0GB
Partition: ID-1: / size: 16G used: 8.4G (57%) fs: ext4 dev: /dev/sda1
ID-2: swap-1 size: 2.15GB used: 0.00GB (0%)
fs: swap dev: /dev/sda2
RAID: No RAID devices: /proc/mdstat, md_mod kernel module present
Sensors: System Temperatures: cpu: 49.0C mobo: N/A
Fan Speeds (in rpm): cpu: N/A
Info: Processes: 181 Uptime: 14 min Memory: 850.6/3860.3MB
Client: Shell (bash) inxi: 2.3.45