@ereborinkorppi I see that error on my pi too, but it doesn’t interfere with operations.

would you be willing to to do a backup of your system using my backup/restore scripts

https://github.com/sdetweil/MagicMirror-backup-restore

and send me the three files. to my email,
sane userid as here at gmail

config.js, custom.css and the module list

to email js files you have to rename to .txt