Guris

Reinstall did not help - settings is still lost on page reload. I enabled extension (only this one) in incognito mode to prevent interference with other extensios and outcome was...

I already tried incognito mode with ONLY React Dev Tools extension - as I mentioned in my previous message. Still the same. Disabling Go Incognito extension didn't help either.

I've enabled dev build you provided. The error still prevails. Where can I find some debug logs, please? It's not present in standard console output in Chrome Dev Tools.

Unfortunatelly there is only one "inspect view" shown. (And there is no extra log found.) Also extension you provided has different id - see the screenshot, please. 

I can only see _Error_ button on extension tile:  And after reloading the page with devTools open this error always occurs:  Inside _background.js_ on lines 43-49 is this...

Hello @larafe1, you're absolutely right. I've tested this and setting was preserved. Good job! Thanks ;-) Unfortunatelly that's not the option for me (with 3rd party cookies enabled). At least...