I agree with you that Newcastle United is not stable this season unlike the way they were last season, this is because they are playing in the Uefa Champions League, and they are not used to such a situation. I think if they don't qualify for the last 16 of the Uefa Champions League they will be consistent in winning matches in the Premier League. Liverpool might be able to get a point from Manchester City at Etihad Stadium because Manchester City is not at their best form this season.
Yes Newcastle are not used to playing in the Champions League, and by playing in the Chmpions League, their schedule becomes much busier than usual. But it was good for them as a very valuable experience, because Necastle is currently a team that has the potential to return to the Champions League next season.
Their focus is divided, and in the Champions League itself I am very sure they will try their best to get a good experience as well. Even though they are now at the bottom of the standings, their chances are still open to qualify for the last 16 of the Champions League.
Restarting their existence in the Champions League will certainly not be easy for Eddie Howe troops, but this will also make them more mature and start to get used to playing against strong clubs. So far, Newcastle performance should be appreciated. If they fail to qualify for the group phase, Newcastle can try again next season. Little by little, Newcastle is reintroducing itself to the Champions League. Regarding its performance in the Premier League last season Newcastle performed normally and was able to secure a ticket, but this season the competition in the top 4 of the Premier League is getting tighter after Liverpool's return, which has slightly changed the atmosphere of the weekend, getting hotter.