How to fix the error "QObject::moveToThread:" in opencv in python?

I got same problem, it was from opencv-python version problem for me.
My Linux machine's environment is as following:

$ cat /etc/lsb-release 
...
DISTRIB_DESCRIPTION="Ubuntu 18.04.5 LTS"
$ date
Tue Aug 11 11:43:16 KST 2020
$ python --version
Python 3.7.8
$ pip list|grep Qt
PyQt5                5.15.0
PyQt5-sip            12.8.0
$ pip list|grep opencv-python
opencv-python        4.3.0.38

I downgraded opencv-python 4.3.0.38 to 4.3.0.36.

$ pip uninstall opencv-python
$ pip install opencv-python==4.3.0.36
$ pip list|grep opencv-python
opencv-python        4.3.0.36

First, uninstall any versions of OpenCV you may have installed. If you installed using pip:

sudo pip uninstall opencv-python

Next, try installing OpenCV using your Linux distro's package manager. For Ubuntu/Debian, this is:

sudo apt-get install libopencv-dev python-opencv

I was able to fix this problem by installing new pyqt.

if you are using anaconda, just write down below:

$ conda install pyqt