Question on an anomaly.

I am currently testing slony slony1-1.1.2 on 3 nodes configured as follows:

node 1                    node 2                  node 3
MASTER ------>  SLAVE1 -------> SLAVE2

All works correctly.
However, I noticed that after doing a switchover to SLAVE1:
==================================
lock set (id = 1, origin = 1);
wait for event (origin = 1, confirmed = 2);
move set (id = 1, old origin = 1, new origin = 2);
wait for event (origin = 1, confirmed = 2);
==================================

slon on SLAVE2 stops.
It can be restarted successfully, but I am wondering if this is
expected behavior, as it is not documented that this will occur.

Why would the other slave(s) stop during a switchover?