Every now and then I am consulted about a situation involving dissatisfaction with how an Estate is being administered. Sometimes it's the Executor who is being challenged and sometimes it's a beneficiary who does not agree with something that the Executor is doing.
Let me start out by saying that almost always the issue is a problem with communication. My encouragement to Executors is to be transparent as much as possible. My encouragement to beneficiaries is to be patient and the talk with the Executor - don't assume they are acting inappropriately. Being an Executor can be a difficult and thankless job.
The other common reason stated by heirs/beneficiaries is a dissatisfaction with what the Will says about the distribution of the property in the Estate. For a discussion about challenging a Will, you can see my article on Challenging a Will.