My original problem was that I kept running into 
during bootup. Usually, I'd just reboot a few times and the error went away. I even tried following these instructions to resolve it, but it did not help. However, recently the error message persisted after quite a number of reboot attempts, so I decided to continue to boot up. Upon bootup, I found that my WiFi isn't connected and the Wifi Networks under the Networking tab said device not ready. I followed this answer and restarted the network manager with sudo systemctl restart network-manager and the Wifi started to work. On the next bootup, even that didn't work. I followed this answer and commented out the lines at /etc/networks/interfaces, restarted network-manager and all the wifi signals disappeared, except the mobile hotspots. I uncommented the lines and the wifi signals reappeared, however, on a reboot, they disappeared again (the lines are still uncommented). Since then, I have been unable to connect or detect my Router's broadcasts and have no other options but to use my mobile hotspots. I even tried reinstalling the wifi drivers as instructed here, but in vain.
Outputs from few commands:
Command: inxi -F
Output:
System: Host: host Kernel: 4.15.0-33-generic x86_64 bits: 64 Desktop: Unity
Distro: Ubuntu 16.04.5 LTS (Xenial Xerus)
Machine: Type: Laptop System: HP product: HP Notebook v: Type1ProductConfigId serial: <root required>
Mobo: HP model: 80C1 v: 96.40 serial: <root required> UEFI [Legacy]: Insyde v: F.1B date: 10/19/2015
Battery: ID-1: BAT1 charge: 21.8 Wh condition: 26.4/41.4 Wh (64%)
CPU: Topology: Dual Core model: Intel Core i3-5005U bits: 64 type: MT MCP L2 cache: 3072 KiB
Speed: 1896 MHz min/max: 500/1900 MHz Core speeds (MHz): 1: 1291 2: 1243 3: 1237 4: 1373
Graphics: Device-1: Intel Broadwell-U Integrated Graphics driver: i915 v: kernel
Display: x11 server: X.Org 1.19.6 driver: modesetting unloaded: fbdev,vesa resolution: 1366x768~60Hz
OpenGL: renderer: Mesa DRI Intel HD Graphics 5500 (Broadwell GT2) v: 4.5 Mesa 18.0.5
Audio: Device-1: Intel Broadwell-U Audio driver: snd_hda_intel
Device-2: Intel Wildcat Point-LP High Definition Audio driver: snd_hda_intel
Sound Server: ALSA v: k4.15.0-33-generic
Network: Device-1: Realtek RTL8101/2/6E PCI Express Fast/Gigabit Ethernet driver: r8169
IF: enp7s0 state: down mac: dc:4a:3e:d1:b0:03
Device-2: Realtek RTL8723BE PCIe Wireless Network Adapter driver: rtl8723be
IF: wlp13s0 state: up mac: 48:e2:44:80:58:95
Drives: Local Storage: total: 931.51 GiB used: 135.44 GiB (14.5%)
ID-1: /dev/sda vendor: Seagate model: ST1000LM024 HN-M101MBB size: 931.51 GiB
Partition: ID-1: / size: 912.91 GiB used: 135.44 GiB (14.8%) fs: ext4 dev: /dev/sda1
ID-2: swap-1 size: 3.92 GiB used: 0 KiB (0.0%) fs: swap dev: /dev/sda5
Sensors: System Temperatures: cpu: 42.0 C mobo: N/A
Fan Speeds (RPM): N/A
Info: Processes: 229 Uptime: 23m Memory: 3.78 GiB used: 1.64 GiB (43.4%) Shell: bash inxi: 3.0.22
Command: lspci
00:00.0 Host bridge: Intel Corporation Broadwell-U Host Bridge -OPI (rev 09)
00:02.0 VGA compatible controller: Intel Corporation Broadwell-U Integrated Graphics (rev 09)
00:03.0 Audio device: Intel Corporation Broadwell-U Audio Controller (rev 09)
00:04.0 Signal processing controller: Intel Corporation Broadwell-U Camarillo Device (rev 09)
00:14.0 USB controller: Intel Corporation Wildcat Point-LP USB xHCI Controller (rev 03)
00:16.0 Communication controller: Intel Corporation Wildcat Point-LP MEI Controller #1 (rev 03)
00:1b.0 Audio device: Intel Corporation Wildcat Point-LP High Definition Audio Controller (rev 03)
00:1c.0 PCI bridge: Intel Corporation Wildcat Point-LP PCI Express Root Port #1 (rev e3)
00:1c.2 PCI bridge: Intel Corporation Wildcat Point-LP PCI Express Root Port #3 (rev e3)
00:1c.5 PCI bridge: Intel Corporation Wildcat Point-LP PCI Express Root Port #6 (rev e3)
00:1d.0 USB controller: Intel Corporation Wildcat Point-LP USB EHCI Controller (rev 03)
00:1f.0 ISA bridge: Intel Corporation Wildcat Point-LP LPC Controller (rev 03)
00:1f.2 SATA controller: Intel Corporation Wildcat Point-LP SATA Controller [AHCI Mode] (rev 03)
00:1f.3 SMBus: Intel Corporation Wildcat Point-LP SMBus Controller (rev 03)
00:1f.6 Signal processing controller: Intel Corporation Wildcat Point-LP Thermal Management Controller (rev 03)
07:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8101/2/6E PCI Express Fast/Gigabit Ethernet controller (rev 07)
0d:00.0 Network controller: Realtek Semiconductor Co., Ltd. RTL8723BE PCIe Wireless Network Adapter
Command: ifconfig && iwconfig
enp7s0 Link encap:Ethernet HWaddr dc:4a:3e:d1:b0:03
UP BROADCAST MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)
lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING MTU:65536 Metric:1
RX packets:1025 errors:0 dropped:0 overruns:0 frame:0
TX packets:1025 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:89243 (89.2 KB) TX bytes:89243 (89.2 KB)
wlp13s0 Link encap:Ethernet HWaddr 48:e2:44:80:58:95
inet addr:192.168.43.144 Bcast:192.168.43.255 Mask:255.255.255.0
inet6 addr: fe80::e692:e7ed:b3cb:3a1a/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:10504 errors:0 dropped:0 overruns:0 frame:0
TX packets:8878 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:6949200 (6.9 MB) TX bytes:1689349 (1.6 MB)
lo no wireless extensions.
enp7s0 no wireless extensions.
wlp13s0 IEEE 802.11 ESSID:"Moto C 6768"
Mode:Managed Frequency:2.412 GHz Access Point: 5E:51:88:FD:7D:5A
Bit Rate=7.2 Mb/s Tx-Power=20 dBm
Retry short limit:7 RTS thr=2347 B Fragment thr:off
Power Management:on
Link Quality=40/70 Signal level=-70 dBm
Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0
Tx excessive retries:0 Invalid misc:8 Missed beacon:0
