Here are a few that I noticed as far as my experience is concerned.
In cross-cultural communication between high and low context people, a lack of understanding may preclude reaching a solution, and a conflict can arise. ( Maybe in cases like sending meeting invites etc)
A typical mistake I frequently see is insufficient risk management. Some PMs tend to create a risk log during the project initiation phase, and then let it "rot". That could also be applied to other logs (e.g. issue log)