When a device does not work properly and the symptoms are not clear it is useful to collect some data and logs from the device. It may be possible to conclude the culprit by investigating those logs.
This help article has scripts (command files) attached, helping the collection of logs greatly. The script does everything for you - it knows where to get the data and how to handle it. The end result is one file, a container.
1) Enable the developer mode in your phone. Please follow these instructions. You need to do this only to get the Terminal app and to set the remote connection (SSH) password (super-user password).
2) Download the file (right-click it and take "save link as")
to your computer and unzip it. Next, copy the resulting collect-logs.sh file to your phone (to "Mass storage", i.e., the default user area pointed to by $HOME).
3) Open the Terminal app on your phone.
4) Set the file permissions with the following command:
chmod 744 collect-logs.sh
Using the script
Open the Terminal app again if not open any more.
5) Run the script with the command:
Type your super-user password if requested.
The script collects the data and includes them to one single file. The file is saved in the home storage area of your phone.
6) Copy the log file
(for instance: basic-logs-2020-06-22-1746.tar)
from your phone to your computer.
If you are in contact with Jolla customer care, send this file to them, please.