There is a new firmware release recently. The new version is 4.22.15190. Give that a try.
https://pgaskin.net/KoboStuff/kobofirmware.html
At that URL, you can download the version for your Kobo and manually install it. Oh and do not go back to any version 4.19. It's too buggy. If you feel the need to go back, try 4.20.14622.
To manually install the firmware, once you have the ZIP file for the firmware, unzip the contents to the .kobo directory and eject the Kobo. It will then proceed to install and reboot.