Summing up for anyone encountering that problem.
1) move this folder to Desktop and restart Premiere Pro:
[win]: C:\Users\%username%\AppData\Roaming\Knights of the Editing Table\excalibur
[mac]: /Users/%username%/Library/Application Support/Knights of the Editing Table/excalibur
if this didn't help
2) move this file to Desktop and restart Premiere Pro:
[win]: C:\Users\%username%\AppData\Roaming\SpellBook\knights_of_the_editing_table.excalibur.json
[mac]: /Users/%username%/Library/Application Support/SpellBook/knights_of_the_editing_table.excalibur.json
note to myself: implement backup for user settings and shortucts