Sql 2012 sp1 update script runs on every switchover ?

Hi all,
Every time I switchover my sql 2012 sp1 db to the other node in my 2 node a/p cluster the sql 2012 sp1 updatescript runs again (without any errors) ?!
If I stop and start on the same node all is ok.

What triggers the sql 2012 update script and how to avoid to run over and over ??

Thx for any help.

acki4711