#3 Wrong team selections
Unai Emery was brought in the club to make them the title contenders they could not become under Arsene Wenger but it looks like the current manager hasn't learned from the mistakes of the former manager.
He has made several mistakes during his time at Arsenal with regards to team selection. Players of the quality of Aaron Ramsey and Mesut Ozil aren't getting much game time when they should be playing the whole game every week. This is one of the reasons why Arsenal couldn't extend Ramsey's contract and as a result, they will lose him in the upcoming transfer window for free.
They have dropped Mesut Ozil many times now and they lack the creativity part when players of this quality aren't part of the starting XI. Mesut Ozil trained for the whole week before the West Ham United game but somehow he wasn't seen fit enough to play any role in the whole match.
If the selection continues to punish Arsenal in their matches by costing them points, not only will they be fighting for a Europa League spot but also Unai Emery will fall out with the fans as well as with Arsenal leadership.