Initially: 
Node 1 is the master. Node 2 is the slave.
There is only one replication set (set ID 1).

Switchover is defined as:
LOCK SET 1.
WAIT FOR EVENT.
MOVE SET 1 from node 1 to node 2.
WAIT FOR EVENT.

I run the switchover script on node 2 to effect a switchover.
After waiting for 1 hour I realize that switchover is stalled. I find
that if I stop and then start the database clients that are connected
to node 1, the switchover may complete successfully.

What are the factors that cause switchover to stall? What are the
factors that help switchover to complete?

Thank you for any guidance in advance.
-Fiel Cabral