Wlan adapter: No Internet access at the nearby of the wlan AccessPoint

Hallo,

since an update of my xubuntu 18.04.2 the onboard Wlan connection to the Internet is not working properly.
If my Notebook is close to the Wlan Access Point, i can't get an Internet access, no Websit, no Ping is anserewd, the wlan Icon shows full strength and IP is assigned. When I go with my Notebook 2 rooms further everything works. Then I go back the same Issue. With an USB Wifi Dongle it works evrything properly, so it is not a Network Problem. With a Live DVD and an Older kernel the onboard Wlan HW works properly, so it is also not a Hardware Problem.
The only diffrence between the two conditions is the antenna Position in the room and the Signal strength see below.

Linux version:
Description: Ubuntu 18.04.2 LTS
Release: 18.04
linux-firmware: 1.173.5
kernel: 4.18.0-18-generic

My Onboard Wlan adapter:

Network controller [0280]: Qualcomm Atheros QCA9377 802.11ac Wireless Network Adapter [168c:0042] (rev 31)
 Subsystem: Lenovo QCA9377 802.11ac Wireless Network Adapter [17aa:0901]
 Kernel driver in use: ath10k_pci
 Kernel modules: ath10k_pci, wl

(Network name is changed by me)

iwconfig close to the Access Point:

lp2s0 IEEE 802.11 ESSID:"MyNetwork"
          Mode:Managed Frequency:2.447 GHz Access Point: 00:00:00:00:00:00
          Bit Rate=1 Mb/s Tx-Power=20 dBm
          Retry short limit:7 RTS thr:off Fragment thr:off
          Power Management:on
          Link Quality=67/70 Signal level=-43 dBm
          Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0
          Tx excessive retries:0 Invalid misc:0 Missed beacon:0

iwconfig two Rooms further:

wlp2s0 IEEE 802.11 ESSID:"MyNetwork"
          Mode:Managed Frequency:2.447 GHz Access Point: 00:00:00:00:00:00
          Bit Rate=1 Mb/s Tx-Power=20 dBm
          Retry short limit:7 RTS thr:off 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:0 Missed beacon:0

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: linux-image-4.18.0-18-generic 4.18.0-18.19~18.04.1
ProcVersionSignature: Ubuntu 4.18.0-18.19~18.04.1-generic 4.18.20
Uname: Linux 4.18.0-18-generic x86_64
NonfreeKernelModules: wl
ApportVersion: 2.20.9-0ubuntu7.6
Architecture: amd64
CurrentDesktop: XFCE
Date: Sun May 12 20:32:27 2019
InstallationDate: Installed on 2018-06-03 (343 days ago)
InstallationMedia: Xubuntu 18.04 LTS "Bionic Beaver" - Release amd64 (20180426)
SourcePackage: linux-signed-hwe
UpgradeStatus: No upgrade log present (probably fresh install)