Error starting new Kernels after a few Hours

[MarkusThill]

Hi,
I am using Jupyter Notebooks for some Deep Learning tasks. Everything is working fine. So I start Jupyter, work on my notebooks, run them, etc.
However, after a few hours (I do not know after how much time, actually) I cannot start new Kernels (I need Python3 Kernels). I get the following error:

Traceback (most recent call last): File "/usr/lib64/python3.6/site-packages/tornado/web.py", line 1592, in _execute result = yield result File "/usr/lib64/python3.6/site-packages/tornado/gen.py", line 1133, in run value = future.result() File "/usr/lib64/python3.6/site-packages/tornado/gen.py", line 1141, in run yielded = self.gen.throw(*exc_info) File "/usr/lib/python3.6/site-packages/notebook/services/sessions/handlers.py", line 73, in post type=mtype)) File "/usr/lib64/python3.6/site-packages/tornado/gen.py", line 1133, in run value = future.result() File "/usr/lib64/python3.6/site-packages/tornado/gen.py", line 1141, in run yielded = self.gen.throw(*exc_info) File "/usr/lib/python3.6/site-packages/notebook/services/sessions/sessionmanager.py", line 79, in create_session kernel_id = yield self.start_kernel_for_session(session_id, path, name, type, kernel_name) File "/usr/lib64/python3.6/site-packages/tornado/gen.py", line 1133, in run value = future.result() File "/usr/lib64/python3.6/site-packages/tornado/gen.py", line 1141, in run yielded = self.gen.throw(*exc_info) File "/usr/lib/python3.6/site-packages/notebook/services/sessions/sessionmanager.py", line 92, in start_kernel_for_session self.kernel_manager.start_kernel(path=kernel_path, kernel_name=kernel_name) File "/usr/lib64/python3.6/site-packages/tornado/gen.py", line 1133, in run value = future.result() File "/usr/lib64/python3.6/site-packages/tornado/gen.py", line 326, in wrapper yielded = next(result) File "/usr/lib/python3.6/site-packages/notebook/services/kernels/kernelmanager.py", line 160, in start_kernel super(MappingKernelManager, self).start_kernel(**kwargs) File "/usr/lib/python3.6/site-packages/jupyter_client/multikernelmanager.py", line 110, in start_kernel km.start_kernel(**kwargs) File "/usr/lib/python3.6/site-packages/jupyter_client/manager.py", line 240, in start_kernel self.write_connection_file() File "/usr/lib/python3.6/site-packages/jupyter_client/connect.py", line 472, in write_connection_file kernel_name=self.kernel_name File "/usr/lib/python3.6/site-packages/jupyter_client/connect.py", line 137, in write_connection_file with open(fname, 'w') as f: FileNotFoundError: [Errno 2] No such file or directory: '/run/user/1132/jupyter/kernel-9a6c897d-2591-4cc2-b3ea-9ac4803a8e55.json'

The comand jupyter kernelspec list delivers:
Available kernels: python3 /usr/share/jupyter/kernels/python3

The directory /run/user/1132/jupyter exists, however the file kernel-9a6c897d-2591-4cc2-b3ea-9ac4803a8e55.json mentioned in the error does not.

jupyter --version
4.4.0

After restarting Jupyter, everything works fine again for some time. Kernels, which are already running do not cause any problems, they will also still run after many days. Only starting new Kernels after some time bothers me a little. Maybe somebody has an idea, what the problem could be. Unfortunately, I do not know which other information could be helpful. So please let me know if I can provide any additional information.