I just see Arsenal repeating same thing they did in the premier league last season, just take a look at how Arsenal started very well this season just to reach this stage and starts losing points. Well, it's obvious that Arsenal may not really be strong enough to stand as title contenders this season so their match against Crystal palace may not be certain to whether they can defeat them regardless of the fact that they are playing in their home ground after all, they lost against Westham in Emirate stadium so it wouldn't be a surprise if Crystal palace also do the same.
Arsenal started this season in excellent form, but now we can say that Arteta is again facing a decline in results. Perhaps Arteta adheres to some kind of training strategy that he considers optimal, and considers these seasonal declines to be some kind of coincidence of unsuccessful games. There is still a difference with last season, since last time the decline was at the end of the season, and this time it happened in the middle. So far they are 5 points behind Liverpool, this is not critical, but winning back this difference will not be easy.